Support hillshade layer in globe with terrain

[birkskyum]

Towards

• [Feat] Support Terrain in Globe projection #4927

This adds support for the hillshade layers in globe+terrain mode.

It can be merged independently of

• Support background layer type on globe with terrain3d #4972

Working on this, I did notice there's still a problem with the fog breaking the globe+terrain mode. The workaround implemented makes the fog color transparent, but is the sky isn't set in the style it ends up making the entire terrain transparent. I made a better solution that passes the globeMode bool to the terrain.frag shader, and simply disables the fog logic in globe mode instead.

Closes #4928

• The unsupported Fog/Horizon is isn't disabled properly on Globe with Terrain3D #4928

• Confirm your changes do not include backports from Mapbox projects (unless with compliant license) - if you are not sure about this, please ask!
• Add an entry to CHANGELOG.md under the ## main section.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 90.45%. Comparing base (e4760d0) to head (7a7ca42).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4976      +/-   ##
==========================================
- Coverage   90.67%   90.45%   -0.22%     
==========================================
  Files         266      266              
  Lines       38170    38178       +8     
  Branches     3208     3153      -55     
==========================================
- Hits        34610    34535      -75     
- Misses       2611     2687      +76     
- Partials      949      956       +7     

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[birkskyum]

closed in favor of #4977