Use pre-commit to invoke ruff, mypy

[khaeru]

See iiasa/message_ix#742. This also includes the job step from iiasa/message-ix-models#124 / iiasa/message-ix-models#127.

Also:

• Drop support, compatibility dependencies, and CI jobs for Python 3.7, which reached EOL 2023-06.
• Work around Track/work around lp:2035206: missing lxml wheel for cp38-macosx #494.

How to review

Read the diff and note that the CI checks all pass.

PR checklist

• Continuous integration checks all ✅
• Add or expand tests; coverage checks both ✅
• Add, expand, or update documentation.
• Update release notes.

[codecov]

Codecov Report

Merging #492 (3333827) into main (3a5479c) will decrease coverage by 0.1%.
The diff coverage is 100.0%.

@@           Coverage Diff           @@
##            main    #492     +/-   ##
=======================================
- Coverage   98.5%   98.5%   -0.1%     
=======================================
  Files         42      42             
  Lines       4557    4554      -3     
=======================================
- Hits        4493    4489      -4     
- Misses        64      65      +1     

Files Changed	Coverage Δ
ixmp/__init__.py	100.0% <100.0%> (ø)

... and 1 file with indirect coverage changes