Fix color deserialization, add schema

[semagnum]

Fixes #1614

Summarize your change.

Fixes color deserialization so it works correctly. Add to documentation schema generator as well.

Reference associated tests.

Adds serialization test for coverage.

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 84.86%. Comparing base (c0e97b0) to head (0244567).
⚠️ Report is 106 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1915      +/-   ##
==========================================
+ Coverage   84.11%   84.86%   +0.74%     
==========================================
  Files         198      181      -17     
  Lines       22241    13054    -9187     
  Branches     4687     1206    -3481     
==========================================
- Hits        18709    11078    -7631     
+ Misses       2610     1790     -820     
+ Partials      922      186     -736     

Flag	Coverage Δ
py-unittests	84.86% <100.00%> (+0.74%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
src/opentimelineio/deserialization.cpp	64.05% <100.00%> (+11.94%)	⬆️
...timelineio/console/autogen_serialized_datamodel.py	79.10% <ø> (+0.58%)	⬆️
...-opentimelineio/opentimelineio/core/_core_utils.py	79.91% <ø> (-6.56%)	⬇️
tests/test_json_backend.py	93.93% <100.00%> (+0.49%)	⬆️

... and 133 files with indirect coverage changes

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