Fix SimpleHistoryAdmin to consistently use AUTH_USER_MODEL in history

[epou]

Description

• Adapt the admin user change view depending on the HistoryRecord.user_model provided (default: AUTH_USER_MODEL) on the admin history view.
• Added ability to track custom user_model with explicit custom history_user_model

Related Issue

#1302

Motivation and Context

The SimpleHistoryAdmin.history_view assumes that the user model associated with the history_user is the one specified in AUTH_USER_MODEL, disregarding any class provided in the HistoricalRecords.user_model argument.

How Has This Been Tested?

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• I have run the pre-commit run command to format and lint.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• I have added my name and/or github handle to AUTHORS.rst
• I have added my change to CHANGES.rst
• All new and existing tests passed.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (f48b53d) 96.87% compared to head (60c006d) 96.86%.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1303      +/-   ##
==========================================
- Coverage   96.87%   96.86%   -0.01%     
==========================================
  Files          23       23              
  Lines        1278     1277       -1     
  Branches      211      211              
==========================================
- Hits         1238     1237       -1     
  Misses         21       21              
  Partials       19       19              

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[MarcinWieczorek]

+1 for this change.