[python] Rename set_reader_coords to set_coords

[johnkerl]

Issue and/or context: As tracked on issue #2407 / [sc-51048].

Note that the intended Python and R API changes are all agreed on and finalized as described in #2407.

Changes:

@nguyenv mentioned the other doing this. However while working on #3244 I realized it was a good deconfuse for me to go ahead and do this sooner than later.

Notes for Reviewer:

[codecov]

Codecov Report

Attention: Patch coverage is 91.66667% with 2 lines in your changes missing coverage. Please review.

Project coverage is 83.90%. Comparing base (50c5d71) to head (ae18f34).
Report is 5 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3253      +/-   ##
==========================================
+ Coverage   83.79%   83.90%   +0.10%     
==========================================
  Files          51       51              
  Lines        5560     5560              
==========================================
+ Hits         4659     4665       +6     
+ Misses        901      895       -6     

Flag	Coverage Δ
python	83.90% <91.66%> (+0.10%)	⬆️

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

Components	Coverage Δ
python_api	83.90% <91.66%> (+0.10%)	⬆️
libtiledbsoma	∅ <ø> (∅)

[nguyenv]

Thank you!