Build CI on more realistic combinations (and faster)

[undermyumbrella1]

Fixes #2898

• builds once
• uploads build artifacts
• other jobs/other java version will download this build artifact
• then it will run compiled tests to check that they pass

Considerations:

1. originally matrix jobs are used

• but this mean other jobs will have to depend on all jobs in the matrix to complete
• instead of a single job in the matrix to complete = slower
• Therefore, reusable workflows is used instead
• so each run will be a separate gh job

2. Android job depends on build job's build artifacts

• specifically Task :androidTest:bundleDebugClassesToRuntimeJar
• is this expected behaviour or should android job be able to run successfully, independent of build job?