[c++] Perf: Make arrow conversion async

[XanthosXanthopoulos]

Issue and/or context: TileDB to Arrow column conversion was single threaded but should be async

Changes:

Notes for Reviewer:

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 85.26%. Comparing base (6a59c3e) to head (212c1fd).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4456      +/-   ##
==========================================
- Coverage   85.27%   85.26%   -0.01%     
==========================================
  Files         136      136              
  Lines       21266    21266              
==========================================
- Hits        18135    18133       -2     
- Misses       3131     3133       +2     

Flag	Coverage Δ
python	88.42% <ø> (-0.03%)	⬇️
r	83.53% <ø> (ø)

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

Components	Coverage Δ
python_api	88.42% <ø> (-0.03%)	⬇️
libtiledbsoma	∅ <ø> (∅)

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