[WIP] CI: 30-40sec install w/ pixi

[ax3l]

Update our unit tests to use:

• Ubuntu 22.04 (from 20.04)
• GCC 12 (from GCC 9)

This speeds up dependency installs significantly.

• many test are too unstable to produce the same checksums and their tolerances need to be bumped
• rebase after Set up CTest #5068 was merged
• some analysis scripts might fail with the SciPy update (i.e., see Update constants to use values from CODATA 2022 #5661)