grails 5.1.2: deploy plugin war: HTTP Status 404 The requested resource is not available

### Expected Behavior

I have a number of plugins that are also stand alone apps. i.e. they have a web user interface, but they also provide services (domain classes) to other grails apps as a plugin. This was all working fine in grails 4. It also works ok in grails 5.1.2 when using `grails run-app`. Where it has now stopped working when upgrading from grails 4 -> grails 5.1.2 is when deploying a war.

### Actual Behaviour

```
HTTP Status 404 – Not Found
Type Status Report

Message The requested resource [/myPlugin512-0.1/] is not available

Description The origin server did not find a current representation for the target resource or is not willing to disclose that one exists.
```

There is absolutely nothing in the way of errors under tomcat. Which was extremely confusing for a long time. It happily deploys the war, but then nothing happens.

### Steps To Reproduce

```
sdk default grails 5.1.2
grails create-plugin myPlugin512
cd myPlugin512
vi build.gradle
```
Now add the ability to create a war:
`apply plugin:"war"`

Now build:
```
./gradlew bootWar
cp build/libs/myPlugin512-0.1.war /c/Programs/Tomcat9/webapps
```

Now try and access your app:
`http://localhost:8080/myPlugin512-0.1/`

Also, I don't think this is related to other Tomcat issues reported here. I tried the `providedRuntime "org.springframework.boot:spring-boot-starter-tomcat"` thing, but it didn't help.

### Environment Information

grails 5.1.2
java zulu 13.0.5-fx
Windows 11
Tomcat 9.0.56

### Example Application

_No response_

### Version

5.1.2

Start with the reproduced build.gradle change and run ./gradlew bootWar, then deploy build/libs/myPlugin512-0.1.war to Tomcat 9.0.56 as described. Compare the Grails 5.1.2 deployment behavior with grails run-app and verify that the application URL serves the plugin app instead of returning HTTP 404.

Written by the indexing model from the issue text.