[Tiered caching] [Milestone 1] Enable serialization for IndicesRequest cache key

[sgup432]

Is your feature request related to a problem? Please describe.
As of now, request cache is a composite key comprising shardId, query object and IndexReader.CacheKey. We need to make it serializable for it to store to disk as part of tiered caching. CacheKey is tightly coupled with lucene which makes it tricky. We essentially need to wrap CacheKey in OpenSearch to be able to solve this.

Refer main issue for more details - #10024
and #10870

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