Support Python 3.11

[khaeru]

Take advantage of genno >= 1.16, in which sparse is an optional/extra dependency.

Previously, via genno → sparse → numba → llvmlite, it was not possible to install/test ixmp with the latest Python; for example, Python 3.11 was released 2022-10-24, but numba 0.57 supporting Python 3.11 was not released until 2023-05-03, a lag of ~6 months.

Notes:

• For Adjust for JPype1 v1.4.1 #463, we forced a downgrade of JPype1 to < 1.4.1. But JPype1 <= 1.4.0 is not available as binary wheels for Python 3.11. This PR does not force this downgrade for Python 3.11—and the tests seem to pass!
• However, an experiment (see this run) confirms that the test failures still occur for Python 3.10, so we retain the workaround.

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. N/A
• Update release notes.

[codecov]

Codecov Report

Merging #481 (bd7b78f) into main (3c922f4) will not change coverage.
The diff coverage is n/a.

@@          Coverage Diff          @@
##            main    #481   +/-   ##
=====================================
  Coverage   98.5%   98.5%           
=====================================
  Files         42      42           
  Lines       4489    4489           
=====================================
  Hits        4425    4425           
  Misses        64      64           

[glatterf42]

Looks good to me.