CI: Micromamba Workflow

[pgierz]

The CI action has a depcrecation, as noted here.

Migrated to use mamba-org/setup-micromamba@v2 instead of mamba-org/provision-with-micromamba in the workflow file.

[pgierz]

This fixes the issue that previously seen in #209 with the conda not getting set up correctly, but there still seems to be an issue with the requirements, at least on macOS.

[pgierz]

OK, I don't 100% like how this was fixed (OpenSSL is apparently painful), but tests pass again.

Nothing on the actual Python side needed to be changed here, this is just for building correctly on the CI runner. If any end-users on MacOS end up with strange import errors with missing shared libraries (libcrypto.so not found), please send them to me and I can fix it once and then with their help write a better section for the documentation.

[koldunovn]

Thanks a lot, Paul!