ci: Add workflow to build and upload Python wheels

[isobelhooper]

Changes:

• New workflow runs when a tag is created, and when there's a push to main.
• Workflow builds Python wheels using maturin, and uses dunamai to make sure that wheels for non-tag pushes have sensible versions (with 'dev' in them as appropriate).
• Workflow also uploads the wheels to our private Python repo.

Still to do:

• Sort out the credentials for the uploads.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (5d213b7) 82.78% compared to head (c4ee567) 83.22%.
Report is 15 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #262      +/-   ##
==========================================
+ Coverage   82.78%   83.22%   +0.44%     
==========================================
  Files          34       34              
  Lines        4234     4232       -2     
  Branches     4149     4116      -33     
==========================================
+ Hits         3505     3522      +17     
+ Misses        542      523      -19     
  Partials      187      187              

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