docker: Add Python 3.13 free-threaded Docker images

[enwask]

Adds an additional base layer for building Python 3.13 from source with disable-gil, and makes the necessary changes to the rest of the build process as well as Docker build workflows.

[enwask]

It would probably be worth adding a run to CI-core which runs the tests with free-threaded Python

Thought about this but I think lots of things will fail off the bat so not sure it should be in CI yet

[EdCaunt]

Thought about this but I think lots of things will fail off the bat so not sure it should be in CI yet

That's a reasonable contention, but they will all need fixing eventually. We've been tripped up like this before (CXX anyone?)

[enwask]

That's a reasonable contention, but they will all need fixing eventually. We've been tripped up like this before (CXX anyone?)

Yeah, just wasn't sure that we want CI to always be red from now on—I think this is above my paygrade though so I'll defer to consensus

[mloubout]

I agree with @EdCaunt that at least one basic test needs to be added to the base no-mpi (i.e., pytest-core-nompi.py, possibly with just test_operator.py). This test file contains very little runtime and mostly just operator build, which should ensure that the base of Devito works with it.

[mloubout]

Looks like it fails to build

https://github.com/devitocodes/devito/actions/runs/16507922396/job/46683232942

[codecov[bot]]

Codecov Report

:white_check_mark: All modified and coverable lines are covered by tests. :white_check_mark: Project coverage is 87.73%. Comparing base (69ffd48) to head (3054e73).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2681      +/-   ##
==========================================
- Coverage   92.10%   87.73%   -4.37%     
==========================================
  Files         248      248              
  Lines       49654    49654              
  Branches     4368     4368              
==========================================
- Hits        45734    43566    -2168     
- Misses       3213     5326    +2113     
- Partials      707      762      +55     

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pytest-gpu-nvc-nvidiaX	?

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[EdCaunt]

Commit history will want a cleanup before merge

[mloubout]

Needs:

https://github.com/cupy/cupy/pull/9149