Add support for Python=3.12

[valeriupredoi]

Once ESMValGroup/ESMValCore#2228 *allowing support for Python=3.12 in ESMValCore), we should see what roadblocks we have here, so am starting early. That Core PR is currently roadblocked only by prospector not being Python=3.12-compatible, but we're working on that.

As of 5 April 2024 - updated issues

• esmvalcore (prospector is the only roadblock there)
• ncl -> issue with builds against later proj's (>=9.3.1) support for proj >=9.3.1 NCAR/ncl#210
• r-akima needs unpinned unpin r-akima #3564
• psy- suite (also at install point they need to move from SafeConfigParser to regular parser, via AttributeError: module 'configparser' has no attribute 'SafeConfigParser' - SafeConfigParser has now been fully retired in 3.12) psy-stuff has now been updated to support 3.12 via @Chilipp good work, see Rebuild for python312 conda-forge/psyplot-feedstock#27 - except psy-reg which still needs a rebuild (with Philipp's new infrastructure)
• prospector (direct dep here, and as we have it via esmvalcore) - needs update some dependency pins so we can build with Python=3.12 landscapeio/prospector#645 that, in turn, needs a fix/workaround of master proposed in Mechanical fix/workaround for tests/tools/pyroma/test_pyroma_tool.py landscapeio/prospector#658
• all else is fine!

[valeriupredoi]

@ESMValGroup/technical-lead-development-team we are inching closer to suppoert Python=3.12 - have a look here https://github.com/ESMValGroup/ESMValTool/actions/runs/8453069262/job/23154935341?pr=3501 - only 4 dependencies need to be rebuilt fro 3.12 - I am a bit at a deadend with prospector though, been waiting on my PR to be merged there since last November; the psy- pkgs I believe that will be updated soon, will go pinch Philipp there; the 🐘 in the room is NCL - am gonna go see what's the atmosphere there; and the pesky one is r-akima - we need to unpin it! 🍺

[valeriupredoi]

OK the issue with NCL is not as bad as I thought - it's compatibility with later proj's see NCAR/ncl#210

[valeriupredoi]

note to self: rerun tests sooner than later, psy-maps only made it to conda-forge just about an hour ago

done 🥳