Add getLayersOrder() to Map and Style

[neodescis]

Launch Checklist

Closes #3277. Adds a getter for Style's _order "private" property to Style and Map.

• 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.
• Include before/after visuals or gifs if this PR includes visual changes.
• Write tests for all new functionality.
• Document any changes to public APIs.
• Post benchmark scores.
• Add an entry to CHANGELOG.md under the ## main section.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (838bb63) 75.23% compared to head (0b89dea) 75.45%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3279      +/-   ##
==========================================
+ Coverage   75.23%   75.45%   +0.21%     
==========================================
  Files         241      241              
  Lines       19256    19260       +4     
  Branches     4339     4339              
==========================================
+ Hits        14488    14532      +44     
+ Misses       4768     4728      -40     

Files	Coverage Δ
src/style/style.ts	84.25% <100.00%> (+0.42%)	⬆️
src/ui/map.ts	83.27% <100.00%> (+0.04%)	⬆️

... and 3 files with indirect coverage changes

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[HarelM]

Mainly nit picking.
Any reason you can think of why this shouldn't be added to the API?
Is there a different workaround with existing API calls? maybe serialize?

[neodescis]

Mainly nit picking. Any reason you can think of why this shouldn't be added to the API? Is there a different workaround with existing API calls? maybe serialize?

See the linked issue I filed. I was originally using getStyle(), but it explicitly excludes "custom" layers. As far as I can tell, there is no other way to get the full order, custom layers included.

Also, FWIW, there is a similar issue filed in mapbox. The suggestion there was to use _order directly, but that felt wrong.

[neodescis]

Thank you @HarelM !