fix(android): defer startup camera change events

[RobJacobson]

Description

Fixes #4213

Android may report a camera change before the map's attachment callbacks apply Camera.defaultSettings. Buffer startup notifications and dispatch one event from the current camera state after those callbacks complete. Subsequent camera changes continue to emit normally. The buffering state lives in a private startupCameraEvents object inside RNMBXMapView.

Reproducer evidence

Using the issue's configured center [-93.265, 44.9778]:

• Before: startup events reported [0, 0], then [-93.265, 44.9778].
• After: the startup event reported [-93.26500000000003, 44.9778]; no [0, 0] event was emitted.

Validation

The original PR head (edb1099) and the refactored implementation (aa3161ff) passed the same ten-scenario Android emulator harness. Both APKs produced identical center/zoom event sequences. Verification used React Native 0.84.1, Mapbox Maps SDK 11.23.1, Fabric, and the Android example app with an empty style.

• Four map mounts each emitted one startup event at the configured center [-93.265, 44.9778] and zoom 6, without an initial [0, 0] event.
• Six further scenarios passed: valid defaults at [0, 0], no Camera, Camera without defaults, controlled camera props alongside defaults, later moves to [0, 0] and Tokyo, and delayed Camera mounting.
• A temporary Kotlin check compared the original helper with the anonymous object extracted from RNMBXMapView. All 4,096 twelve-operation sequences of camera-change notifications and readiness calls matched.
• ./gradlew :app:assembleDebug :rnmapbox_maps:testDebugUnitTest -PreactNativeArchitectures=arm64-v8a passed, including all 11 remaining native unit tests.
• node node_modules/jest/bin/jest.js --runInBand passed all 164 tests across 25 suites.
• ESLint completed without errors; existing warnings remain.

The issue report's React Native 0.83.6 and Mapbox Maps SDK 11.20.1 were not rerun. Temporary verification code and configuration are excluded from the commit.

Checklist

• I've read CONTRIBUTING.md.
• I updated the doc/other generated code with running yarn generate in the root folder (not applicable to this native-only change).
• I have tested the new feature on /example app.
  • In V11 mode/iOS
  • In New Architecture mode/iOS
  • In V11 mode/Android
  • In New Architecture mode/Android
• I added/updated a sample - if a new feature was implemented (bug fix; no sample API added).

Screenshot OR Video

This is a native event timing fix; emulator logs above show the before/after behavior.

Component to reproduce the issue

<Mapbox.MapView
  style={{ flex: 1 }}
  onCameraChanged={(event) => {
    const [longitude, latitude] = event.properties.center;
    console.log(`COORDS ->> lng: ${longitude} lat: ${latitude}`);
  }}
>
  <Mapbox.Camera
    defaultSettings={{ centerCoordinate: [-93.265, 44.9778] }}
  />
</Mapbox.MapView>

[mfazekas]

Thanks, this fixes #4213; we verified it on an emulator, including no-Camera, delayed Camera, re-attach and pans during startup. Splitting this out of RNMBXMapView makes sense, but a separate file and test for two flags is more than it needs; please make it a private anonymous object in RNMBXMapView (private val startupCameraEvents = object { … } calling sendCameraChangedEvents() directly) and drop CameraChangeEventGate.kt and its test. Please also shorten the attach comment to one line, e.g. // Camera.addToMap applies defaultSettings in the attach callbacks (#4213).