[python] Parallelize pybind11 build [RFC]

[johnkerl]

Issue and/or context: Found while working on issue #2407 / [sc-51048].

Changes:

To speed up iterative dev time, I have separate little aliases & scripts (available on request). One of them is to parallelize pybind11 builds as they are sequential. It turns out those that there is an option to do this within setup.py.

See also https://pybind11.readthedocs.io/en/stable/compiling.html.

Notes for Reviewer:

To make this work we'd need to include pybind11 as an explicit dependency ...

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 89.79%. Comparing base (11d5396) to head (3b26fa8).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3031      +/-   ##
==========================================
+ Coverage   89.64%   89.79%   +0.14%     
==========================================
  Files          40       40              
  Lines        4096     4096              
==========================================
+ Hits         3672     3678       +6     
+ Misses        424      418       -6     

Flag	Coverage Δ
python	89.79% <ø> (+0.14%)	⬆️

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

Components	Coverage Δ
python_api	89.79% <ø> (+0.14%)	⬆️
libtiledbsoma	∅ <ø> (∅)