[c++/python] Improve Metadata API

[XanthosXanthopoulos]

Issue and/or context: Improve the Metadata API by automating type casting to commonly used types

Changes:

Notes for Reviewer:

[codecov]

Codecov Report

❌ Patch coverage is 52.00000% with 36 lines in your changes missing coverage. Please review.
✅ Project coverage is 85.22%. Comparing base (fc739b6) to head (6a1123e).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4461      +/-   ##
==========================================
- Coverage   85.28%   85.22%   -0.06%     
==========================================
  Files         136      136              
  Lines       21266    21214      -52     
==========================================
- Hits        18136    18079      -57     
- Misses       3130     3135       +5     

Flag	Coverage Δ
python	88.35% <96.55%> (-0.11%)	⬇️
r	83.50% <23.91%> (-0.03%)	⬇️

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

Components	Coverage Δ
python_api	88.35% <96.55%> (-0.11%)	⬇️
libtiledbsoma	∅ <ø> (∅)

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[jp-dark]

This looks great! Thanks!