Change geojson source API to use promises

[HarelM]

Change the geojson source API from using callbacks to using promises.
Also changed the examples to use that and verified that they work.

[codecov-commenter]

Codecov Report

Attention: 27 lines in your changes are missing coverage. Please review.

Comparison is base (10af384) 75.50% compared to head (6e70163) 75.56%.
Report is 13 commits behind head on main.

Files	Patch %	Lines
src/source/rtl_text_plugin_worker.ts	59.09%	9 Missing ⚠️
src/source/worker.ts	35.71%	9 Missing ⚠️
src/source/geojson_source.ts	0.00%	6 Missing ⚠️
src/data/bucket/symbol_bucket.ts	66.66%	1 Missing ⚠️
src/style/evaluation_parameters.ts	50.00%	1 Missing ⚠️
src/symbol/transform_text.ts	66.66%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3421      +/-   ##
==========================================
+ Coverage   75.50%   75.56%   +0.05%     
==========================================
  Files         241      242       +1     
  Lines       19230    19201      -29     
  Branches     4271     4259      -12     
==========================================
- Hits        14520    14509      -11     
+ Misses       4710     4692      -18     

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