feat(PointAnnotationManager): multiple managers with independent slots & properties

[mfazekas]

Description

Builds on #4209. Previously there was a single shared point annotation manager per MapView, so the <PointAnnotationManager slot> introduced in #4209 could only configure that one manager — two managers with different slots was impossible.

Now each <PointAnnotationManager> owns its own Mapbox annotation layer, so multiple managers can sit in different slots of the Standard style. PointAnnotations associate with a manager by being its direct children. Bare PointAnnotations (not wrapped in a manager) keep working via a default manager — fully backwards compatible. A manager can be flagged default to configure the slot/properties used by those bare annotations.

<MapView styleURL="mapbox://styles/mapbox/standard">
  {/* configures the manager used by bare annotations */}
  <PointAnnotationManager default slot="middle" />
  <PointAnnotation id="bare" coordinate={[lng, lat]}>…</PointAnnotation>

  <PointAnnotationManager slot="top" iconAllowOverlap>
    <PointAnnotation id="a" coordinate={[lng, lat]}>…</PointAnnotation>
  </PointAnnotationManager>
  <PointAnnotationManager slot="bottom">
    <PointAnnotation id="b" coordinate={[lng, lat]}>…</PointAnnotation>
  </PointAnnotationManager>
</MapView>

New manager props: id, default, slot, iconAllowOverlap, iconIgnorePlacement, iconOptional, textAllowOverlap, textIgnorePlacement, textOptional.

Implementation notes:

• iOS: per-component RNMBXPointAnnotationManager with its own layer id (auto-generated by the SDK unless id is set); tap / long-press / deselect are routed across all registered managers; children mounted via Fabric.
• Android: per-component RNMBXPointAnnotationCoordinator with its own layer id; click/drag routed across all coordinators; children wired through the view manager.
• A bare PointAnnotation resolves to the default manager, which is what a default-flagged <PointAnnotationManager> configures.

Checklist

• I've read CONTRIBUTING.md
• I updated the doc/other generated code with running yarn generate in the root folder
• 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 (/example)

Screenshot OR Video

Example Annotations › PointAnnotationManager Multiple, on the iOS simulator (New Architecture). Two managers in different slots over a pitched 3D view of Lower Manhattan: the slot="bottom" pins (red B) render behind the Standard style's 3D buildings while the slot="top" pins (blue T) render in front — z-ordering that a single shared manager could not produce. Android compiles (Kotlin); runtime not yet exercised.

Component to reproduce

See example/src/examples/Annotations/PointAnnotationManagerMultiple.tsx.