HBase 30024 tiered exclusive topology

[VladRodionov]

Summary

This PR adds a compatibility bridge from the existing BlockCache API to the new CacheEngine abstraction.

TieredExclusiveTopology and TopologyBackedCacheAccessService operate on CacheEngine instances, but the existing production cache implementations such as LruBlockCache, BucketCache, TinyLfuBlockCache, and LruAdaptiveBlockCache still implement BlockCache. BlockCacheBackedCacheEngine allows these legacy cache implementations to participate in topology-backed cache wiring before they are migrated to implement CacheEngine directly.

This is an incremental migration step. It does not change production cache wiring and does not remove or replace CombinedBlockCache.

Changes

• Adds BlockCacheBackedCacheEngine, a CacheEngine adapter backed by an existing BlockCache.
• Adds CacheEngines helper factory for creating CacheEngine instances from legacy BlockCache instances.
• Adds unit tests for adapter delegation and null validation.
• Adds tests proving that TopologyBackedCacheAccessService can operate through TieredExclusiveTopology using BlockCache-backed engines.

Migration path

The new cache architecture is moving toward:

CacheAccessService
  -> CacheTopology
      -> CacheEngine(s)

AI assistance disclosure

This PR was prepared with assistance from ChatGPT. All changes were reviewed, tested, and submitted by the author.