Gradle build script improvements

[TWiStErRob]

A step towards #2898

This is in preparation for an other PR introducing toolchains which is a cross-module configuration. I did some generalization and consistency improvements to make it easier to make global changes. Some of the diffs in the PR might look strange, I recommend looking commit by commit to make sense of them.

Many modules already had java-library.gradle included. So I created a parallel java-test.gradle. With this there's now two named types of modules. Each subproject belongs to one of these types, except:

• androidTest is an Android module, very special (because no java plugin)
• bom is published, but not a library

There are some special-setup modules which still extend one of the named modules:

• rootProject/mockito-core is a java-library (among many other things).
• groovyInlineTest and groovyTest are Groovy modules too.
• kotlinReleaseCoroutinesTest and kotlinTest are Kotlin modules too.
• osgi-test does things.

There were several (test) modules missing Java compatiblility declaration:

• Now they're all using Java 11 source/target for compilation.

Testing:

• Generate repo snapshot by changing

  -repositories { maven { url = "$buildDir/repo" } }
  +repositories { maven { url = "${rootProject.buildDir}/repo" } }
  

• Running gradlew clean followed by gradlew publishAllPublicationsToMavenRepository --no-build-cache
• Grab contents of rootProject/build/repo/
• Rename all files that have timestamps replacing timestamp with a constant.
  Test matrix:
• I repeated this on master with JAVA_HOME=JDK11, JAVA_HOME=JDK17.
• and on the branch with JAVA_HOME=JDK11, JAVA_HOME=JDK17.
• and on the branch with JAVA_HOME=JDK17 + -Pmockito.test.java=11

The changes all looked expected. Diffs were:

• javadoc timestamps
• Maven metadata (SNAPSHOT timestamps and artifact order)
• Java 11 and 17 generate the same decompiled classes, but different class files and constant pools. This is on master already.

Checklist

• Read the contributing guide
• PR should be motivated, i.e. what does it fix, why, and if relevant how
• If possible / relevant include an example in the description, that could help all readers
  including project members to get a better picture of the change
• Avoid other runtime dependencies
• Meaningful commit history ; intention is important please rebase your commit history so that each
  commit is meaningful and help the people that will explore a change in 2 years
• The pull request follows coding style
• Mention Fixes #<issue number> in the description if relevant
• At least one commit should mention Fixes #<issue number> if relevant

[codecov-commenter]

Codecov Report

Patch and project coverage have no change.

Comparison is base (69e0a6c) 85.45% compared to head (4c303f9) 85.45%.

Additional details and impacted files

@@            Coverage Diff            @@
##               main    #3062   +/-   ##
=========================================
  Coverage     85.45%   85.45%           
  Complexity     2888     2888           
=========================================
  Files           329      329           
  Lines          8801     8801           
  Branches       1093     1093           
=========================================
  Hits           7521     7521           
  Misses          992      992           
  Partials        288      288           

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[TimvdLippe]

Awesome. Thanks!