Fix system and template generator for Espaloma 0.3.*

[ijpulidos]

Created a new PR with these changes such that we can use the CI secrets from our repo. Supersedes #271

These changes add template_generator_kwargs to the system generators.

Resolves #245 . Resolves #263 . Resolves #282

TODO

• add tests

[codecov-commenter]

Codecov Report

Attention: 24 lines in your changes are missing coverage. Please review.

Comparison is base (3970498) 69.35% compared to head (b3b2886) 67.95%.

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Additional details and impacted files

@@            Coverage Diff             @@
##             main     #293      +/-   ##
==========================================
- Coverage   69.35%   67.95%   -1.40%     
==========================================
  Files           5        5              
  Lines         855      877      +22     
==========================================
+ Hits          593      596       +3     
- Misses        262      281      +19     

Files	Coverage Δ
openmmforcefields/generators/system_generators.py	50.87% <100.00%> (+0.28%)	⬆️
...penmmforcefields/generators/template_generators.py	72.88% <17.24%> (-2.20%)	⬇️

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[jchodera]

@mikemhenry @ijpulidos : I've finished cleaning up the docs and running local tests.
After this passes tests, can you merge and cut a new release?