additional tests for patterns, mixins, and abstract classes.

[cmungall]

Ensure owlgen doesn't pun when literal constraints are applied
to slots that are translated to ObjectProperties. Fixes #1841

[codecov]

Codecov Report

Attention: Patch coverage is 66.66667% with 1 lines in your changes are missing coverage. Please review.

Project coverage is 80.30%. Comparing base (c5b6b8c) to head (f00f521).
Report is 25 commits behind head on main.

Files	Patch %	Lines
linkml/generators/owlgen.py	66.66%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1947      +/-   ##
==========================================
+ Coverage   80.15%   80.30%   +0.14%     
==========================================
  Files         100       99       -1     
  Lines       11537    11293     -244     
  Branches     2914     2854      -60     
==========================================
- Hits         9248     9069     -179     
+ Misses       1741     1684      -57     
+ Partials      548      540       -8     

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