feat: DH-21259: Add map_style to theme

[jnumainville]

This doesn't really block deephaven/deephaven-plugins#1279 but is used for it.
I do think it's best to allow anyone to override the map_style in the theme if we want it to be allowed in the theme, although this method is a bit wonky so I'm not sure if it's the best way to do it.

[mofojed]

Looks good. Updates when changing the theme too, nice.
Fix up the unit tests first, may just need to update the snapshots. To do that, run npm test, then it'll say 2 tests failed because of snapshots, press u to update failing snapshots.
Pretty sure it's just the added map style property that's causing it to fail.

[codecov]

Codecov Report

❌ Patch coverage is 0% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 45.71%. Comparing base (7b2a23e) to head (3079716).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
packages/code-studio/src/styleguide/colorUtils.ts	0.00%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2605      +/-   ##
==========================================
- Coverage   45.71%   45.71%   -0.01%     
==========================================
  Files         771      771              
  Lines       43649    43652       +3     
  Branches    11046    11231     +185     
==========================================
  Hits        19954    19954              
- Misses      23678    23681       +3     
  Partials       17       17              

Flag	Coverage Δ
unit	45.71% <0.00%> (-0.01%)	⬇️

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