WIP: Upgrade and un-pin dependencies and Python version to use

[dalonsoa]

Description

Update the whole codebase and tests to enable MUSE running with more modern Python versions, pandas and xarray. So far, due to the versions used of pandas and xarray we were limited to using Python 3.9, at most.

Things to do:

• [x] Unpin dependencies in pyproject.toml
• [x] Add modern python to workflow files
• [x] Review the code to avoid errors
• [ ] Review the code to ensure tests pass
• [ ] Make sure that notebooks and tutorials still produce the right results (requires researchers intervention)

Fixes #120

Type of change

Please add a line in the relevant section of CHANGELOG.md to document the change (include PR #) - note reverse order of PR #s.

• [ ] New feature (non-breaking change which adds functionality)
• [ ] Optimization (non-breaking, back-end change that speeds up the code)
• [x] Bug fix (non-breaking change which fixes an issue)
• [x] Breaking change (whatever its nature)

Key checklist

• [ ] All tests pass: $ python -m pytest
• [ ] The documentation builds and looks OK: $ python -m sphinx -b html docs docs/build

Further checks

• [ ] Code is commented, particularly in hard-to-understand areas
• [ ] Tests added that prove fix is effective or that feature works