feat: implement `cols_reorder()` for flexible column reordering

[jrycw]

Hello team,

This PR introduces cols_reorder(), allowing users to reorder columns in a specified order easily.

While the existing move_*() functions are useful for repositioning a few columns, they don't provide fine-grained control over column order. I've often had to rely on Pandas or Polars for this task. The implementation of this function follows a straightforward approach, similar to the existing move_*() functions.

Feedback is always welcome!😊

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 90.00000% with 1 line in your changes missing coverage. Please review.

Project coverage is 90.86%. Comparing base (dc82197) to head (60d43ce). Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
great_tables/_spanners.py	87.50%	1 Missing :warning:

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #625      +/-   ##
==========================================
+ Coverage   90.85%   90.86%   +0.01%     
==========================================
  Files          46       46              
  Lines        5423     5432       +9     
==========================================
+ Hits         4927     4936       +9     
  Misses        496      496              

:umbrella: View full report in Codecov by Sentry.
:loudspeaker: Have feedback on the report? Share it here.