Replace miniconda by micromamba in CI

[aperezhortal]

This PR takes #256 one step further using the mamba-org/provision-with-micromamba@main action to create the environment, instead of conda-incubator/setup-miniconda@v2

Although the computational time saved is minimal (a minute at the most), it simplifies a little bit the workflow specification, condensing the previous "miniconda installation" and "environment creation" task into a single one.

More information on micromamba: https://github.com/mamba-org/mamba#micromamba

[codecov]

Codecov Report

Merging #257 (092e0e8) into master (7213c95) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #257   +/-   ##
=======================================
  Coverage   80.92%   80.92%           
=======================================
  Files         142      142           
  Lines       10759    10759           
=======================================
  Hits         8707     8707           
  Misses       2052     2052           

Flag	Coverage Δ
unit_tests	80.92% <ø> (ø)

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[dnerini]

Ah this is real nice, I didn't know about a micromamba!

[kmuehlbauer]

@aperezhortal Nice, I was just doing the same over at h5netcdf, but using the old style downloading via snakepit (as wradlib does). And then I see this new provisioning thing popping up in your commits. That saved me quite some keyboard time. Just wanted to say thanks 😀

[dnerini]

@aperezhortal you wanna merge this or is it still work in progress?