Run E2E Gradle tests on Docker

What does this MR do and why?

This changes the implementation of the Gradle E2E spec to run the Gradle package publishing and installation in a Docker container. The previous implementation relied on creating a pipeline to publish and then install a package using Gradle.

The idea here is that we can improve flakiness by skipping the pipeline and directly running the package upload/download command from a docker container.

Another improvement in this MR is to reduce unnecessary resource allocations - e.g. create the project deploy token only on the context where we test the project deploy token.

The old pipeline-based implementation was retained to CI job token scenario.

References

#550594 (closed)

Screenshots or screen recordings

NA

How to set up and validate locally

Run the spec rspec qa/specs/features/browser_ui/5_package/package_registry/maven_gradle_repository_spec.rb against local GDK

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