Remove compilers dependency from conda environment and force install x64 git in OSX Github Action workflows

[valeriupredoi]

Description

Closes #2419

compilers was added by @bouweandela four years ago in #603 - see #603 (comment) - I don't think we still need it but may be worth checking the docker build goes well without it anyway

OSX tests: failing with "setuptools_scm._run_cmd.CommandNotFoundError: git" - this has been seen in ESMValGroup/ESMValTool#3581 and it's not hitting just this node, but rather, it's an endemic issue related to macOS 14 on arm64:

  Image: macos-14-arm64
  Version: 20240422.3
  Included Software: https://github.com/actions/runner-images/blob/macos-14-arm64/20240422.3/images/macos/macos-14-arm64-Readme.md
  Image Release: https://github.com/actions/runner-images/releases/tag/macos-14-arm64%2F20240422.3

For some reason, the system git goes fishing when the x64 environment is activated and used - @schlunma and I had a decent debate about it in the linked Tool PR - no time to really-really understand the issue, just plop a git installer in the workflow!

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 94.51%. Comparing base (6786bd9) to head (9741e3a).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2420   +/-   ##
=======================================
  Coverage   94.51%   94.51%           
=======================================
  Files         246      246           
  Lines       14023    14023           
=======================================
  Hits        13254    13254           
  Misses        769      769           

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[bouweandela]

Looks fine to me @valeriupredoi, could you clean up a bit?

The compilers package was needed a long time ago, when we were still installing most packages from PyPI and only those that weren't on PyPI from conda.

[valeriupredoi]

Thanky, bud 🍺