feat: Enhance LaTeX output tables by adding support for the stub and row groups

[rich-iannone]

This PR adds improved LaTeX rendering support for GT(rowname_col=), GT(groupname_col=), and .tab_options(row_group_as_column=). As these options heavily interact, all combinations of parameters were accounted for and checked (plus snapshot tests were added after visual verification).

Basic stub with row labels (top), Non-stub layout with row groups (bottom):

Row groups and stub (with row labels):

Two column stub layout using .tab_options(row_group_as_column=True):

One-column stub using .tab_options(row_group_as_column=True) with no row names:

Table with other structural features (title and source note):

Fixes: #783

[codecov]

Codecov Report

❌ Patch coverage is 96.00000% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 91.60%. Comparing base (85d25f6) to head (31c3114).

Files with missing lines	Patch %	Lines
great_tables/_utils_render_latex.py	96.00%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #784      +/-   ##
==========================================
+ Coverage   91.58%   91.60%   +0.02%     
==========================================
  Files          47       47              
  Lines        5752     5791      +39     
==========================================
+ Hits         5268     5305      +37     
- Misses        484      486       +2     

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