Update to AmberTools23

[jchodera]

AmberTools23 includes a new GAFF version (2.2.20, March 2021). From the header:

AMBER General Force Field for organic molecules (Version 2.2.20, March 2021)

We should add this GAFF version and update other force fields we are able to.

[mattwthompson]

The short version of the current plan is

1. Make a 0.13.0 that doesn't have GAFF support (Temporarily remove GAFF because of parmchk2 issues #329)
   a. Point users towards 0.12.0 which still does, with limitations (Python 3.10, AmberTools 22, x86 architecture only)
   a. These limitations don't apply to the SMIRNOFF template generator
2. Make a 0.14.0 that relies on Allow multiple registrations of the same atom type if definitions identical openmm#4531
   a. This should work with Python 3.10-3.12, AmberTools 22-23, x64 and Apple Silicon
3. When AmberTools 24 is packaged, test this package alongside it
   b. Currently expect it to work (no new GAFF version) but hard to predict prior to testing

[mattwthompson]

I think this is done? @mikemhenry