[query] Move LoweredTableReaderCoercer into ExecuteContext

[ehigham]

Refactored table reader coercion and caching mechanism.

What changed?

• Removed shouldCacheQueryInfo method from Backend class
• Introduced CoercerCache in ExecuteContext
• Refactored LoweredTableReader.makeCoercer to return a function instead of a class
• Removed local caching in GenericTableValue and LoweredTableReader
• Added NoCaching utility

Why make this change?

This change aims to optimize table reader coercion by:

• Centralizing caching logic in ExecuteContext
• Allowing more flexible caching strategies across different backend implementations

[ehigham]

Warning

This pull request is not mergeable via GitHub because a downstack PR is open. Once all requirements are satisfied, merge this PR as a stack on Graphite.
Learn more

• [query] Lowering + Optimisation with implict timing context #14731 : 2 dependent PRs (#14732 , #14748 )
• [query] Lift backend state into {Service|Py4J}BackendApi #14698
• [query] Move LoweredTableReaderCoercer into ExecuteContext #14696 👈 (View in Graphite)
• [query] unify backend rpc #14693
• [query] Remove persistedIr from Backend interface #14692
• [query] Remove lookupOrCompileCachedFunction from Backend interface #14691
• [query] Remove BlockMatrix persist from Backend interface #14690
• [query] Expose references via ExecuteContext #14686
• [query] Extract Backend Methods called from Python into Py4JBackendExtensions #14767
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