Added buildSrclibrary conventions and language based configurations.

- Updated to Gradle 8 (JAVA-5756)
- Removed `util:taglets` as now in `buildSrc`.
- Moved `util:spock` into `driver-core` as the annotation is now shared via `testArtifacts`.
- Added optional support (JAVA-5757)

Migrated tests to work with conventions:

- Refactored `JsonPoweredTestHelper` to handle either local and jar based resources
- Refactored test cases to use new `JsonPoweredTestHelper.getTestDocuments` method
- Refactored test cases to normalize usage of loading test data
- Moved scala / kotlin integration tests into a standardized `integerationTest` directory

Update github action and put version in `gradle.properties`.

JAVA-5756
JAVA-5757
JAVA-5758