build: Allow building of python 3.11 environments

This PR unpins xgboost, moves zuko to conda-forge, lets python>=3.8 and allows making of 3.11 environments. We cannot make 3.12 environments due to the fact that there are no wheels for awkward1 for 3.12. We can build awkward1 from source via installing it from pip (tested locally on my M1 laptop) and then we can also make 3.12 envs but no need to for now. The awkward<2 pin is because coffea 0.7.15 thinks it's compatible with awkward2 and if you let that unpinned, conda install a stupid environment with coffea 0.7.15, awkward 2.6.8 and python 3.12 which of course doesn't work.

@magalli I tested the CQR locally on my laptop with a ~half million events root file with xgboost 1.5, 1.6, 1.7 and 2.1 and it takes about 1 minute and 15 seconds with all of them. I'm not seeing any slowdown with xgboost>1.5.1. Any comments on how did you see the slowdown?