Update GHA & CI

[jGaboardi]

This PR:

• overhauls unittests.yml & CI environments
  • use micromamba for Python setup (cuts down runtime dramatically)
  • trim down OS/Python version matrix (no more overkill)
  • only need to test Python 3.9/Ubuntu for base and dev (bleeding edge libpysal)
• overhauls build_docs.yml and adds manual build trigger
• overhauls release_and_publish.yml

Once this PR is merged, we will need to cut a release to be included in the summer PySAL meta-release.

[pedrovma]

Thank you so much, @jGaboardi !

[jGaboardi]

Thank you so much, @jGaboardi !

My pleasure. If you like, I'll go ahead and cut a release today. And if you want me to do that, should it be:

• v1.2.3 or
• v1.3.0

I can just add the version bump to this PR, btw.

[pedrovma]

Thank you so much, @jGaboardi !

My pleasure. If you like, I'll go ahead and cut a release today. And if you want me to do that, should it be:

* [x]  `v1.2.3` or

* [ ]  `v1.3.0`

I can just add the version bump to this PR, btw.

Super! 1.2.3, please. Thanks!