Gitlab build cache improvements

[randomanderson]

What Does This Do

Improves the gradle build cache when running the build in gitlab. The setup closely matches that of CircleCI.

There are 2 caches: a dependency cache and build cache. The dependency cache contains the gradle wrapper and all maven dependencies. The build cache is a cache of the currently running pipeline. Both caches can be controlled on a per-job basis using variables.

Motivation

Fixing the cache is important for #6837 .

Additional Notes

https://github.com/DataDog/auto_inject/pull/172 must be merged before this to use the proper gitlab runners.

[randomanderson]

Converting to a draft while I investigate more tweaks

[github-actions[bot]]

This pull request has been marked as stale because it has not had activity over the past quarter. It will be closed in 7 days if no further activity occurs. Feel free to reopen the PR if you are still working on it.

[github-actions[bot]]

This pull request has been closed because it has not had activity over the past quarter. Feel free to reopen the PR if you are still working on it.