Add support for doSetRollbackOnly in SpannerTransactionManager

**Describe the bug**

When i am in a transaction and it throws an exception, it will catch the exception in
`TransactionAspectSupport.invokeWithinTransaction` and try to rollback

```
try {
// This is an around advice: Invoke the next interceptor in the chain.
// This will normally result in a target object being invoked.
retVal = invocation.proceedWithInvocation();
}
catch (Throwable ex) {
// target invocation exception
completeTransactionAfterThrowing(txInfo, ex);
throw ex;
}
```

This will eventually call
```
Set the given transaction rollback-only. Only called on rollback if the current transaction participates in an existing one.
The default implementation throws an IllegalTransactionStateException, assuming that participating in existing transactions is generally not supported. Subclasses are of course encouraged to provide such support.
Params:
status – the status representation of the transaction
Throws:
TransactionException – in case of system errors
protected void doSetRollbackOnly(DefaultTransactionStatus status) throws TransactionException {
throw new IllegalTransactionStateException(
"Participating in existing transactions is not supported - when 'isExistingTransaction' " +
"returns true, appropriate 'doSetRollbackOnly' behavior must be provided");
}
```

In other transaction managers such as [JpaTransactionManager](https://github.com/spring-projects/spring-framework/blob/7b14606d92bfe36fea048137e794cfff18e9e42a/spring-orm/src/main/java/org/springframework/orm/jpa/JpaTransactionManager.java#L608C69-L608C69)
they set the rollback only flag which seems to cause the transaction to be rolled back.
```
@Override
protected void doSetRollbackOnly(DefaultTransactionStatus status) {
JpaTransactionObject txObject = (JpaTransactionObject) status.getTransaction();
if (status.isDebug()) {
logger.debug("Setting JPA transaction on EntityManager [" +
txObject.getEntityManagerHolder().getEntityManager() + "] rollback-only");
}
txObject.setRollbackOnly();
}
```
It would seem like SpannerTransactionManager should implement something similar.
I initially filed a bug with Spring [issue 31615](https://github.com/spring-projects/spring-framework/issues/31615), they sound happy to help resolve the issue.
Related to issues:
[spring-gcp issue 907](https://github.com/GoogleCloudPlatform/spring-cloud-gcp/issues/907)

See the callstack below:
```
doSetRollbackOnly:1207, AbstractPlatformTransactionManager (org.springframework.transaction.support)
processRollback:844, AbstractPlatformTransactionManager (org.springframework.transaction.support)
rollback:809, AbstractPlatformTransactionManager (org.springframework.transaction.support)
completeTransactionAfterThrowing:678, TransactionAspectSupport (org.springframework.transaction.interceptor)
invokeWithinTransaction:395, TransactionAspectSupport (org.springframework.transaction.interceptor)
invoke:119, TransactionInterceptor (org.springframework.transaction.interceptor)
proceed:184, ReflectiveMethodInvocation (org.springframework.aop.framework)
proceed:751, CglibAopProxy$CglibMethodInvocation (org.springframework.aop.framework)
intercept:703, CglibAopProxy$DynamicAdvisedInterceptor (org.springframework.aop.framework)
deleteProjectReason:-1, ProjectServiceImpl$$SpringCGLIB$$0 (com.my.project.service)
lambda 'shouldThrow' in 'delete project reason that doesn't exists':124, ProjectsIntegrationTest (com.my.project)
shouldThrow:129, ProjectsIntegrationTest (com.my.project)
delete project reason that doesn't exists:124, ProjectsIntegrationTest (com.my.project)
invoke0:-1, NativeMethodAccessorImpl (jdk.internal.reflect)
invoke:77, NativeMethodAccessorImpl (jdk.internal.reflect)
invoke:43, DelegatingMethodAccessorImpl (jdk.internal.reflect)
invoke:568, Method (java.lang.reflect)
invokeMethod:727, ReflectionUtils (org.junit.platform.commons.util)
proceed:60, MethodInvocation (org.junit.jupiter.engine.execution)
proceed:131, InvocationInterceptorChain$ValidatingInvocation (org.junit.jupiter.engine.execution)
intercept:156, TimeoutExtension (org.junit.jupiter.engine.extension)
interceptTestableMethod:147, TimeoutExtension (org.junit.jupiter.engine.extension)
interceptTestMethod:86, TimeoutExtension (org.junit.jupiter.engine.extension)
apply:-1, TestMethodTestDescriptor$$Lambda$233/0x00000237d5151a40 (org.junit.jupiter.engine.descriptor)
lambda$ofVoidMethod$0:103, InterceptingExecutableInvoker$ReflectiveInterceptorCall (org.junit.jupiter.engine.execution)
apply:-1, InterceptingExecutableInvoker$ReflectiveInterceptorCall$$Lambda$234/0x00000237d5151e60 (org.junit.jupiter.engine.execution)
lambda$invoke$0:93, InterceptingExecutableInvoker (org.junit.jupiter.engine.execution)
apply:-1, InterceptingExecutableInvoker$$Lambda$543/0x00000237d52be498 (org.junit.jupiter.engine.execution)
proceed:106, InvocationInterceptorChain$InterceptedInvocation (org.junit.jupiter.engine.execution)
proceed:64, InvocationInterceptorChain (org.junit.jupiter.engine.execution)
chainAndInvoke:45, InvocationInterceptorChain (org.junit.jupiter.engine.execution)
invoke:37, InvocationInterceptorChain (org.junit.jupiter.engine.execution)
invoke:92, InterceptingExecutableInvoker (org.junit.jupiter.engine.execution)
invoke:86, InterceptingExecutableInvoker (org.junit.jupiter.engine.execution)
lambda$invokeTestMethod$7:217, TestMethodTestDescriptor (org.junit.jupiter.engine.descriptor)
execute:-1, TestMethodTestDescriptor$$Lambda$3131/0x00000237d630d240 (org.junit.jupiter.engine.descriptor)
execute:73, ThrowableCollector (org.junit.platform.engine.support.hierarchical)
invokeTestMethod:213, TestMethodTestDescriptor (org.junit.jupiter.engine.descriptor)
execute:138, TestMethodTestDescriptor (org.junit.jupiter.engine.descriptor)
execute:68, TestMethodTestDescriptor (org.junit.jupiter.engine.descriptor)
lambda$executeRecursively$6:151, NodeTestTask (org.junit.platform.engine.support.hierarchical)
execute:-1, NodeTestTask$$Lambda$339/0x00000237d516e698 (org.junit.platform.engine.support.hierarchical)
execute:73, ThrowableCollector (org.junit.platform.engine.support.hierarchical)
lambda$executeRecursively$8:141, NodeTestTask (org.junit.platform.engine.support.hierarchical)
invoke:-1, NodeTestTask$$Lambda$338/0x00000237d516e470 (org.junit.platform.engine.support.hierarchical)
around:137, Node (org.junit.platform.engine.support.hierarchical)
lambda$executeRecursively$9:139, NodeTestTask (org.junit.platform.engine.support.hierarchical)
execute:-1, NodeTestTask$$Lambda$337/0x00000237d516e048 (org.junit.platform.engine.support.hierarchical)
execute:73, ThrowableCollector (org.junit.platform.engine.support.hierarchical)
executeRecursively:138, NodeTestTask (org.junit.platform.engine.support.hierarchical)
execute:95, NodeTestTask (org.junit.platform.engine.support.hierarchical)
accept:-1, SameThreadHierarchicalTestExecutorService$$Lambda$343/0x00000237d516f1b0 (org.junit.platform.engine.support.hierarchical)
forEach:1511, ArrayList (java.util)
invokeAll:41, SameThreadHierarchicalTestExecutorService (org.junit.platform.engine.support.hierarchical)
lambda$executeRecursively$6:155, NodeTestTask (org.junit.platform.engine.support.hierarchical)
execute:-1, NodeTestTask$$Lambda$339/0x00000237d516e698 (org.junit.platform.engine.support.hierarchical)
execute:73, ThrowableCollector (org.junit.platform.engine.support.hierarchical)
lambda$executeRecursively$8:141, NodeTestTask (org.junit.platform.engine.support.hierarchical)
invoke:-1, NodeTestTask$$Lambda$338/0x00000237d516e470 (org.junit.platform.engine.support.hierarchical)
around:137, Node (org.junit.platform.engine.support.hierarchical)
lambda$executeRecursively$9:139, NodeTestTask (org.junit.platform.engine.support.hierarchical)
execute:-1, NodeTestTask$$Lambda$337/0x00000237d516e048 (org.junit.platform.engine.support.hierarchical)
execute:73, ThrowableCollector (org.junit.platform.engine.support.hierarchical)
executeRecursively:138, NodeTestTask (org.junit.platform.engine.support.hierarchical)
execute:95, NodeTestTask (org.junit.platform.engine.support.hierarchical)
accept:-1, SameThreadHierarchicalTestExecutorService$$Lambda$343/0x00000237d516f1b0 (org.junit.platform.engine.support.hierarchical)
forEach:1511, ArrayList (java.util)
invokeAll:41, SameThreadHierarchicalTestExecutorService (org.junit.platform.engine.support.hierarchical)
lambda$executeRecursively$6:155, NodeTestTask (org.junit.platform.engine.support.hierarchical)
execute:-1, NodeTestTask$$Lambda$339/0x00000237d516e698 (org.junit.platform.engine.support.hierarchical)
execute:73, ThrowableCollector (org.junit.platform.engine.support.hierarchical)
lambda$executeRecursively$8:141, NodeTestTask (org.junit.platform.engine.support.hierarchical)
invoke:-1, NodeTestTask$$Lambda$338/0x00000237d516e470 (org.junit.platform.engine.support.hierarchical)
around:137, Node (org.junit.platform.engine.support.hierarchical)
lambda$executeRecursively$9:139, NodeTestTask (org.junit.platform.engine.support.hierarchical)
execute:-1, NodeTestTask$$Lambda$337/0x00000237d516e048 (org.junit.platform.engine.support.hierarchical)
execute:73, ThrowableCollector (org.junit.platform.engine.support.hierarchical)
executeRecursively:138, NodeTestTask (org.junit.platform.engine.support.hierarchical)
execute:95, NodeTestTask (org.junit.platform.engine.support.hierarchical)
submit:35, SameThreadHierarchicalTestExecutorService (org.junit.platform.engine.support.hierarchical)
execute:57, HierarchicalTestExecutor (org.junit.platform.engine.support.hierarchical)
execute:54, HierarchicalTestEngine (org.junit.platform.engine.support.hierarchical)
execute:147, EngineExecutionOrchestrator (org.junit.platform.launcher.core)
execute:127, EngineExecutionOrchestrator (org.junit.platform.launcher.core)
execute:90, EngineExecutionOrchestrator (org.junit.platform.launcher.core)
lambda$execute$0:55, EngineExecutionOrchestrator (org.junit.platform.launcher.core)
accept:-1, EngineExecutionOrchestrator$$Lambda$291/0x00000237d515caf0 (org.junit.platform.launcher.core)
withInterceptedStreams:102, EngineExecutionOrchestrator (org.junit.platform.launcher.core)
execute:54, EngineExecutionOrchestrator (org.junit.platform.launcher.core)
execute:114, DefaultLauncher (org.junit.platform.launcher.core)
execute:86, DefaultLauncher (org.junit.platform.launcher.core)
execute:86, DefaultLauncherSession$DelegatingLauncher (org.junit.platform.launcher.core)
processAllTestClasses:119, JUnitPlatformTestClassProcessor$CollectAllTestClassesExecutor (org.gradle.api.internal.tasks.testing.junitplatform)
access$000:94, JUnitPlatformTestClassProcessor$CollectAllTestClassesExecutor (org.gradle.api.internal.tasks.testing.junitplatform)
stop:89, JUnitPlatformTestClassProcessor (org.gradle.api.internal.tasks.testing.junitplatform)
stop:62, SuiteTestClassProcessor (org.gradle.api.internal.tasks.testing)
invoke0:-1, NativeMethodAccessorImpl (jdk.internal.reflect)
invoke:77, NativeMethodAccessorImpl (jdk.internal.reflect)
invoke:43, DelegatingMethodAccessorImpl (jdk.internal.reflect)
invoke:568, Method (java.lang.reflect)
dispatch:36, ReflectionDispatch (org.gradle.internal.dispatch)
dispatch:24, ReflectionDispatch (org.gradle.internal.dispatch)
dispatch:33, ContextClassLoaderDispatch (org.gradle.internal.dispatch)
invoke:94, ProxyDispatchAdapter$DispatchingInvocationHandler (org.gradle.internal.dispatch)
stop:-1, $Proxy5 (jdk.proxy2)
run:193, TestWorker$3 (org.gradle.api.internal.tasks.testing.worker)
executeAndMaintainThreadName:129, TestWorker (org.gradle.api.internal.tasks.testing.worker)
execute:100, TestWorker (org.gradle.api.internal.tasks.testing.worker)
execute:60, TestWorker (org.gradle.api.internal.tasks.testing.worker)
execute:56, ActionExecutionWorker (org.gradle.process.internal.worker.child)
call:113, SystemApplicationClassLoaderWorker (org.gradle.process.internal.worker.child)
call:65, SystemApplicationClassLoaderWorker (org.gradle.process.internal.worker.child)
run:69, GradleWorkerMain (worker.org.gradle.process.internal.worker)
main:74, GradleWorkerMain (worker.org.gradle.process.internal.worker)
```

Find SpannerTransactionManager and inspect its transaction-status handling, then compare the analogous doSetRollbackOnly implementation in JpaTransactionManager. Trace the rollback path described in the call stack and identify the relevant existing tests or test entry points. Done means an exception in a participating transaction marks the Spanner transaction rollback-only instead of raising the unsupported-operation error.

Written by the indexing model from the issue text.