Add OpenMP support to Mac builds and wheels

[jobovy]

No description provided.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 99.91%. Comparing base (1e3bcd3) to head (fa740c5).
Report is 22 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #660   +/-   ##
=======================================
  Coverage   99.91%   99.91%           
=======================================
  Files         200      200           
  Lines       29260    29269    +9     
  Branches      563      563           
=======================================
+ Hits        29234    29243    +9     
  Misses         26       26           

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[jobovy]

Difficult to avoid the issue with combining conda-numpy and pip-galpy, so approach taken here is to detect and warn about the issue, falling back on non-C version of galpy.

Supersedes and thus closes #651.