[python/r/c++] Bulk-sync main to release-1.15

[johnkerl]

Brings main to release-1.15 en masse, excepting (as usual) apis/r/NEWS.md and apis/r/DESCRIPTION -- but without #3389.

[codecov]

Codecov Report

Attention: Patch coverage is 91.52542% with 20 lines in your changes missing coverage. Please review.

Project coverage is 86.09%. Comparing base (44b317b) to head (7181f50).
Report is 3 commits behind head on release-1.15.

Additional details and impacted files

@@               Coverage Diff                @@
##           release-1.15    #3411      +/-   ##
================================================
+ Coverage         85.87%   86.09%   +0.22%     
================================================
  Files                55       55              
  Lines              6143     6221      +78     
================================================
+ Hits               5275     5356      +81     
+ Misses              868      865       -3     

Flag	Coverage Δ
python	86.09% <91.52%> (+0.22%)	⬆️

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

Components	Coverage Δ
python_api	86.09% <91.66%> (+0.22%)	⬆️
libtiledbsoma	∅ <ø> (∅)

[johnkerl]

This might not work -- since we reverted C++ 20 changes on the release-1.15 branch but not main. I'll need to run individual backport PRs, or re-apply #3389.