(Android) Introduce android build-artifacts' packaging (.aar, source, docs)

[d4vidi]

Description:

Introduce maven publishing for Android: Packaging of artifacts into a predefined @root folder, that's accessible in end-projects using the detox library.
This is the first step in introducing the entire feature (see issue #1323), which would include:

1. Migrating the example projects to using .aar, all-the-while integrating them into the CI as downstream builds.
2. Actual invocation of the packaging in the publishing flow in CI (so that the .arr's etc will be published to npm).