Android: setOverrideSynchronousUpdate for existing sources

[systemed]

#4092 replaced setGeoJsonSync on Android with a new .withSynchronousUpdate(true) option when creating a new GeoJSONSource.

However, this removed the possibility to use synchronous updates for existing GeoJSON sources defined in the stylesheet. Previously we could write:

val turnSource = map.style?.getSource("turn_highlights") as GeoJsonSource? ?: return
turnSource.setGeoJsonSync(FeatureCollection.fromFeatures(lines))

which is no longer possible.

This PR reinstates this possibility by giving the user the option to override the synchronous updates setting for a GeoJSON source. With this, we can write:

val turnSource = map.style?.getSource("turn_highlights") as GeoJsonSource? ?: return
turnSource.setOverrideSynchronousUpdate(true)
turnSource.setGeoJson(FeatureCollection.fromFeatures(lines))

This fixes #4187 using the approach I described in the comment and subsequently commented on by @louwers. I've chosen to fix it at the code level, rather than the stylesheet level, because this is a matter of client implementation rather than map style - in other words, it's very possible that one client using a given stylesheet might want synchronous updates, and another might not.

I've tested it locally using a special build of cycle.travel's app and it works well for me.

AI disclosure: I wrote the code and text myself, but did ask Claude to verify if I'd missed anything along the way, because it's better at C++ than I am. ;)

[louwers]

LGTM, @alexcristici maybe you can also have a look.

[github-actions]

Bloaty Results 🐋

Compared to main

    FILE SIZE        VM SIZE    
 --------------  -------------- 
  +0.0% +4.95Ki  +0.0%    +376    TOTAL

Full report: https://maplibre-native.s3.eu-central-1.amazonaws.com/bloaty-results/pr-4366-compared-to-main.txt

Compared to d387090 (legacy)

    FILE SIZE        VM SIZE    
 --------------  -------------- 
   +51% +59.1Mi  +467% +27.9Mi    TOTAL

Full report: https://maplibre-native.s3.eu-central-1.amazonaws.com/bloaty-results/pr-4366-compared-to-legacy.txt

[github-actions]

Benchmark Results ⚡

Benchmark                                                     Time             CPU      Time Old      Time New       CPU Old       CPU New
------------------------------------------------------------------------------------------------------------------------------------------
OVERALL_GEOMEAN                                            -0.0007         -0.0002             0             0             0             0

Full report: https://maplibre-native.s3.eu-central-1.amazonaws.com/benchmark-results/pr-4366-compared-to-main.txt

[github-actions]

Bloaty Results (iOS) 🐋

Compared to main

    FILE SIZE        VM SIZE    
 --------------  -------------- 
  [ = ]       0  [ = ]       0    TOTAL

Full report: https://maplibre-native.s3.eu-central-1.amazonaws.com/bloaty-results-ios/pr-4366-compared-to-main.txt