copy over PhysicsAnalysis/Algorithms from 21.2

Originally I had tried sweeping/cherry-picking this from 21.2, but with all the three-way merges and commits that involve other packages/directories that was rather painful, so this is now just a direct copy from the current state in 21.2.

Just as with the sweeps, this is all code that was already reviewed for 21.2, and I'd rather keep the number of changes in this MR to a minimum.

These are all new packages, so CI tests won't do anything yet. The plan is to use this as a basis for integrating these into AnalysisBase one package at a time.