Avoid setting marker opacity twice

[erasta]

When creating a marker setOpacity was called twice, which results in calling _updateOpacity twice.
Also the opacity params are check twice for undefined.
This minor optimization solves the above.

Launch Checklist

• 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.
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• Write tests for all new functionality.
• Document any changes to public APIs.
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• Add an entry to CHANGELOG.md under the ## main section.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 91.94%. Comparing base (cc9f170) to head (c3302c0).
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #5441      +/-   ##
==========================================
- Coverage   91.95%   91.94%   -0.01%     
==========================================
  Files         282      282              
  Lines       39050    39049       -1     
  Branches     6863     6862       -1     
==========================================
- Hits        35907    35904       -3     
- Misses       3016     3017       +1     
- Partials      127      128       +1     

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[HarelM]

Thanks for taking the time to fix this.
I've added a few minor comments.

[HarelM]

I think this method can be simplified even further:

this._opacity = opacity !== undefined ? opacity : '1';
this._opacityWhenCovered = opacityWhenCovered!== undefined ? opacityWhenCovered : '0.2';

[erasta]

In the case of calling marker.setOpacity(something);:

• the expected result is that this._opacityWhenCovered will not be changed
• in the suggested code it will reset it to the default '0.2'

same goes for calling marker.setOpacity(undefined, something);

I agree that a oneliner shortening is possible, but it will be somewhat less-understandable.