Update CI to LCG_97python3, add more install/update recipes

Pushing to start the CI tests - I tried two nontrivial workflows, these are running.

I'll wait for some plots before merging, but unless something pops up this will be a recommended upgrade (still to do: check what this means for https://gitlab.cern.ch/cp3-cms/bamboo/-/merge_requests/20 , and also rebase https://gitlab.cern.ch/cp3-cms/bamboo/-/merge_requests/88 to make sure)