feat(collections,clustering): complete Kotlin migration for core modules and apply optimizations

[dkhawk]

Summary

1. Complete Kotlin Migration for Core Library Modules & Tests: Converted all remaining Java source files across :library and :data to idiomatic, safe Kotlin (KmlUrlSanitizer, MapObjectManager, MarkerManager, CircleManager, GroundOverlayManager, PolygonManager, PolylineManager, KmlZipBombTest, StaticClusterTest).
2. Comprehensive Unit Test Suites with Google Truth: Added robust, literate-programming unit tests covering previously untested collection managers, algorithm adapters, projections, and ClusterManager lifecycle operations (MapObjectManagerTest, MarkerManagerTest, CircleManagerTest, GroundOverlayManagerTest, PolygonManagerTest, PolylineManagerTest, NonHierarchicalViewBasedAlgorithmTest, ScreenBasedAlgorithmAdapterTest, GridBasedAlgorithmTest, AbstractAlgorithmTest, SphericalMercatorProjectionTest, StaticClusterTest, ClusterManagerTest).
3. Clean Kotlin Idioms & Optimizations:
   • Replaced !! force-unwraps with safe checks and .also { ... }.
   • Replaced escaped keyword parameters (`object`) with descriptive parameter names.
   • Replaced java.util collection instantiations with pure Kotlin collection builders (mutableMapOf(), mutableSetOf()).
   • Simplified delegating methods to concise single-line expression bodies (=).
   • Optimized loops in HeatmapTileProvider.kt raster calculations.
   • Removed redundant open modality modifiers in ClusterManager.kt.

Verification

./gradlew test lint assemble jacocoTestDebugUnitTestReport — all 265 test tasks, lint checks, and coverage reports succeeded (88.28% coverage on :library, 30.53% on :clustering).

Reviewer

cc @LoyalAbbas

[googlemaps-bot]

Code Coverage

Overall Project	50.4% -0.48%	🍏
Files changed	81.52%	🍏

Module	Coverage
library	89.03% -4.45%	🍏
heatmaps	84.07% -0.19%	🍏
clustering	30.53%	🍏

Files

Module	File	Coverage
library	PolyUtil.kt	97.87%	🍏
	MapObjectManager.kt	92.12% -6.85%	🍏
	CircleManager.kt	78.9% -18.35%	🍏
	GroundOverlayManager.kt	78.9% -18.35%	🍏
	PolylineManager.kt	78.9% -18.35%	🍏
	PolygonManager.kt	78.9% -18.35%	🍏
	MarkerManager.kt	78.16% -20.89%	🍏
heatmaps	HeatmapTileProvider.kt	84.39% -0.27%	🍏
clustering	ClusterManager.kt	68.5%	🍏

[kikoso]

It seems that this got lost during a merge or rebase on the big refactor branch.

The addAll/showAll/hideAll boilerplate (and the checkNotNull fix itself) is duplicated near-verbatim across all 5 manager classes rather than factored into the shared MapObjectManager.Collection base. Maybe we could unify this.

[dkhawk]

Thank you for the review, @kikoso!

The shared boilerplate across the 5 collection managers has now been unified into MapObjectManager.Collection:

• showAll() & hideAll(): Factored into the base MapObjectManager.Collection using a polymorphic protected open fun setVisible(mapObject: O, visible: Boolean).
• checkAndAdd(): Consolidated the null check and addition into a single helper in the base collection.
• addAll(): Factored generic batch-addition helpers (addAll(opts, adder) and addAll(opts, defaultVisible, adder)) into the base collection.
• Subclasses: CircleManager, PolygonManager, PolylineManager, GroundOverlayManager, and MarkerManager now inherit these methods directly with minimal delegate wrappers.
• Tests: Expanded MapObjectManagerTest to directly verify showAll, hideAll, addAll, and checkAndAdd, with :library module unit test coverage increasing to 89.03%.