Add AnyDictionary and AnyVector support for V2d and Box2d

[peter-targett]

Fixes #1714

Summarize your change.

Add Imath V2d and Box2d types so they can be added as metadata in AnyDictionary and AnyVector containers.

Reference associated tests.

Add basic tests for V2d and Box2d to serializable object tests. Also, adapt the composable object test, to test metadata serialization.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 81.66%. Comparing base (c0e97b0) to head (4ae2fec).
Report is 29 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1811      +/-   ##
==========================================
- Coverage   84.11%   81.66%   -2.46%     
==========================================
  Files         198      176      -22     
  Lines       22241    12679    -9562     
  Branches     4687     2791    -1896     
==========================================
- Hits        18709    10354    -8355     
+ Misses       2610     1786     -824     
+ Partials      922      539     -383     

Flag	Coverage Δ
py-unittests	81.66% <100.00%> (-2.46%)	⬇️

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

Files with missing lines	Coverage Δ
...melineio/opentimelineio-bindings/otio_bindings.cpp	98.47% <100.00%> (+0.11%)	⬆️
...ntimelineio/opentimelineio-bindings/otio_utils.cpp	70.10% <100.00%> (+3.43%)	⬆️
tests/test_composable.py	92.59% <100.00%> (ø)
tests/test_serializable_object.py	93.37% <100.00%> (+0.33%)	⬆️

... and 120 files with indirect coverage changes

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