targetExcludeFilename

I'm going to speculate this is not the most efficient

```kts
java {
targetExclude("**/TransactionBeanPostProcessorTest.java")
licenseHeader(copyright + javaLicense)
cleanthat().addMutators(listOf("SafeAndConsensual", "SafeButNotConsensual"))
}
```

I'd rather just write this, which would match that filename specifically.

```kts
targetExcludeFiles("TransactionBeanPostProcessorTest.java")
```

I have a problem where cleanThat can't currently handle java 21 code, and so I'm trying to make spotless skip it.