Changes query terrain elevation to return elevation above mean sea level

[HarelM]

Launch Checklist

This is a replacement of

• Return above-sea-level elevation from queryTerrainElevation + Pass lowered mercator matrix to custom layer #3854
  Which fixes:
• map.queryTerrainElevation not returning expected values #3736

It changes the queryTerrainElevation to return the elevation above mean sea level if the terrain is loaded.
This caused confusion in the past.
Fixes #3736

• Confirm your changes do not include backports from Mapbox projects (unless with compliant license) - if you are not sure about this, please ask!
• Briefly describe the changes in this PR.
• Link to related issues.
• Write tests for all new functionality.
• Document any changes to public APIs.
• 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 87.94%. Comparing base (0ffa890) to head (3d057ef).
Report is 37 commits behind head on main.

✅ All tests successful. No failed tests found.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4876      +/-   ##
==========================================
+ Coverage   87.77%   87.94%   +0.16%     
==========================================
  Files         265      265              
  Lines       37970    37966       -4     
  Branches     2446     2412      -34     
==========================================
+ Hits        33328    33389      +61     
+ Misses       3568     3521      -47     
+ Partials     1074     1056      -18     

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[sbachinin]

There was also a question about terrain exaggeration raised in the previous PR.
That is, in my branch queryTerrainElevation was returning the altitude distorted by exaggeration. I suppose users rather expect that this method will return pure altitude. (But I might be wrong).