Restore Python url_utils module

[darbyjohnston]

PR #2021 removed the url_utils package as part of transitioning .otioz support to C++. However url_utils was part of the public Python API and may be used by other code (e.g., #1664). This PR restores the module and also replaces Python code with C++ functionality where applicable.

Note that the file_bundle_utils.py was also removed as part of the C++ support. This seems unlikely it was ever used outside of the otioz/otiod adapters, so I did not restore it.

Assisted-by: Claude:claude-opus-4-7 [code-review] [debugging]

[codecov-commenter]

Codecov Report

❌ Patch coverage is 92.10526% with 3 lines in your changes missing coverage. Please review.
✅ Project coverage is 83.43%. Comparing base (0eebd21) to head (993dfbc).

Files with missing lines	Patch %	Lines
tests/test_url_conversions.py	90.00%	1 Missing and 1 partial ⚠️
...timelineio/opentimelineio-bindings/otio_bundle.cpp	66.66%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2034      +/-   ##
==========================================
+ Coverage   83.21%   83.43%   +0.21%     
==========================================
  Files         180      182       +2     
  Lines       13465    13503      +38     
  Branches     1253     1254       +1     
==========================================
+ Hits        11205    11266      +61     
+ Misses       2088     2064      -24     
- Partials      172      173       +1     

Flag	Coverage Δ
py-unittests	83.43% <92.10%> (+0.21%)	⬆️

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Files with missing lines	Coverage Δ
src/py-opentimelineio/opentimelineio/__init__.py	100.00% <ø> (ø)
src/py-opentimelineio/opentimelineio/url_utils.py	100.00% <100.00%> (ø)
...timelineio/opentimelineio-bindings/otio_bundle.cpp	68.88% <66.66%> (-0.16%)	⬇️
tests/test_url_conversions.py	90.00% <90.00%> (ø)

... and 1 file with indirect coverage changes

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