tau physval monitoring: merge TauHistUtils into TauDQA, and start cleanup

Hello,

This MR is moving PHYSVAL monitoring code from TauHistUtils to TauDQA.
For no good reason, code was stored in 2 separate packages.
The TauHistUtils package is therefore deleted.

Minimal cleanup was also made. In general, BDT plots were either dropped or replaced with RNN equivalents.
BDT tau ID will no longer be supported in R22.
BDT electron veto is now superseded with an RNN.

More cleanup will come in a follow up MR.

Cheers,
Bertrand