fix: release GoogleMap listeners and dispose subcomposition when showing/hiding map

[dkhawk]

Summary

Fixes memory retention and teardown ordering issues when GoogleMap is repeatedly shown/hidden (if (showMap) { GoogleMap(...) }) or deactivated/reused via ReusableContentHost / LazyColumn:

1. Detach GoogleMap Listeners and InfoWindowAdapter on Clear:
   • MapApplier.attachClickListeners() registers 9 click/drag listeners and ComposeInfoWindowAdapter(mapView, ...) on GoogleMap (wrapped in Binder stubs that hold strong references to MapApplier and MapView), but MapApplier.onClear() never detached them. Added MapApplier.detachClickListeners() and invoked it from onClear().
   • MapPropertiesNode.onRemoved() and onCleared() now clear the 4 camera listeners (setOnCameraIdleListener(null), setOnCameraMoveCanceledListener(null), setOnCameraMoveStartedListener(null), setOnCameraMoveListener(null)) and setLocationSource(null) in addition to cameraPositionState.setMap(null).
   • TileOverlayNode.onRemoved() and onCleared() now clear tileOverlayState.tileOverlay = null.
2. Synchronous Subcomposition Disposal & MapView Teardown:
   • Scoped subcompositionJob and subcomposition (Composition) to MapTagData on the MapView instance so onReset and onRelease dispose the map subcomposition synchronously before lifecycleObserver.moveToDestroyedState() (mapView.onDestroy()) is invoked, and so update cleanly re-launches the subcomposition when a deactivated MapView is reused.
   • Switched launchSubcomposition to Dispatchers.Main.immediate and guarded after mapView.awaitMap() (if (!isActive || mapView.tagDataOrNull !== tagData) return@launch) so rapid show/hide cycles where onRelease runs before getMapAsync completes do not throw a NullPointerException on mapView.tag or create an orphaned Composition.
   • Cleaned up removeOnAttachStateChangeListener, lifecycle observer registration, setViewTreeLifecycleOwner(null), setViewTreeSavedStateRegistryOwner(null), and removeAllViews() in onRelease.

Testing

• Added unit tests in MapApplierCleanupTest verifying that MapApplier.onClear(), MapPropertiesNode, TileOverlayNode, and MarkerNode detach all listeners, InfoWindowAdapter, LocationSource, and state references.
• Added instrumentation tests testShowingHidingMapRepeatedlyReleasesMapViews and testReusableContentHostResetAndReuse in GoogleMapViewTests.
• Verified with heap dump (hprof) analysis across 30 show/hide cycles that 0 GoogleMap / MapApplier / ComposeInfoWindowAdapter instances remain in the heap.

Fixes #581

[github-actions]

Coverage (unit tests)

Compared against 0bc6ecd on main (#1040).

Module	Line %	Change	Branch %	Change
maps-compose	12.09%	🔺 +12.09	2.19%	🔺 +2.19
maps-compose-utils	2.06%	no change	0.49%	no change
maps-compose-widgets	0.00%	no change	0.00%	no change
TOTAL	9.44%	🔺 +9.02	1.82%	🔺 +1.73

_{Line and branch coverage from unit test reports. History is recorded on the coverage-history branch after each merge to main.}

[googlemaps-bot]

Coverage (instrumentation tests)

Overall Project	44.77% -0.06%	🍏
Files changed	91.54%	🍏

Module	Coverage
maps-app	63.91% -0.16%	🍏

Files

Module	File	Coverage
maps-app	MapUpdater.kt	81.62% -0.44%	🍏
	GoogleMap.kt	80.47% -0.55%	🍏
	MapApplier.kt	41.21%	🍏
	TileOverlay.kt	0% -2.52%	❌