First Pass Documentation (docstrings) For Process Folder

[AFg6K7h4fhy2]

This pull request includes a first pass for:

• Correction and or modifications of existing docstrings in ./model/src/pyrenew/process
• Addition of new docstrings in ./model/src/pyrenew/process

Other relevant PRs: (closed: #73 , #74 , #76 )

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 90.57%. Comparing base (20a0384) to head (8390c1d).

Additional details and impacted files

@@           Coverage Diff           @@
##             main      #87   +/-   ##
=======================================
  Coverage   90.57%   90.57%           
=======================================
  Files          28       28           
  Lines         552      552           
=======================================
  Hits          500      500           
  Misses         52       52           

Flag	Coverage Δ
unittests	90.57% <100.00%> (ø)

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[gvegayon]

Just one minor fix (I believe).