Merge #2926: [GA] Overhaul Github Actions Workflow

3ba861c [GA] Overhaul Github Actions Workflow (Fuzzbawls)

Pull request description:

  This is a major overhaul of our GitHub Actions workflow file that introduces several cleanups and optimizations, as well as new jobs dedicated to running just the python functional test suite. Below are some of the more notable changes:

  - Split off functional tests to their own jobs. Often times we will see a trivial failure in one of the functional tests. Prior to this change, this meant needing to re-run the entire build job again. With this change, we can trigger a re-run of just the functional test suite without needing to re-compile the wallet again. This is handled by creating a minimal archive "artifact" in the build job, and passing it to the new functional test jobs. Credit goes to @Duddino for coming up with this idea and doing much of the initial research and testing!
  - Split old configure/build/unittest groupings into their own steps. Instead of exclusively relying on older group macros in a single step, I've created new more descriptive steps to improve readability and responsiveness of the actions report portal. This also helps in seeing where any significant bottle-neck is for a particular job configuration.
  - Unify the `apt_get` and `brew_install` matrix config params. These two params have been unified to just `packages` across all matrix configurations.
  - No longer cache the sapling params. Since the sapling params files are part of our source tree anyways, caching them in GitHub Actions cache files is redundant and only serves to waste valuable cache storage space.
  - Add some basic descriptive commentary for jobs. Self-explanatory.

  Note: The minimalist build artifacts are ONLY intended to be used within the GitHub Actions environment and expire after 5 days from their creation. Failing functional tests that are not resolved within this expiry time will necessitate a full re-run of the workflow. Any use of these artifacts outside of GitHub Actions is discouraged and unsupported.

  ---
  Reviewer's note: GitHub will report this PR as not having all the "required checks" as passing as the names/IDs of jobs have been changed. Once this PR is merged it will be then possible to update the repository settings to reflect the new job names/IDs in the "required checks" settings.

ACKs for top commit: 3ba861c
  Duddino:
    ACK 3ba861c
  panleone:
    utACK 3ba861c

Tree-SHA512: f5d7ff65c5dd37dc24c64dfa47038126923c92146a1fd61410e902cb452e350b49d65a9c8a55c1281b412713825ffc8d794d275519c632e4e2b541b0339cc54a