Support cache expression filter pushdown JOIN

[peterxcli]

This pull request significantly refactors and improves the query condition cache optimizer and filter logic. The main changes focus on making cache filter injection more robust and flexible, improving performance, and enhancing debuggability. The optimizer now more accurately associates cache filters with table scans, supports better statistics-based pruning, and provides improved utilities for cache key handling and introspection.

Key changes include:

Query Condition Cache Optimizer Refactor:

• Replaced the previous single-pass optimizer walk with a two-phase approach: first collecting all LogicalGet nodes, then associating and injecting cache filters based on filter expressions and table bindings. This allows for more robust and accurate cache filter injection. [1] [2]
• Changed the cache filter injection mechanism to use a new InjectCacheExpression method, which ensures the ROW_ID column is present and attaches the filter directly to the correct scan node. [1] [2] [3]
• Improved handling of filter expressions by extracting table bindings and associating expressions only with the correct tables, supporting more complex query plans.

Cache Filter and Key Enhancements:

• Updated CacheExpressionFilter to store and display its associated CacheKey, and added a ToString method for easier debugging and introspection. [1] [2]
• Modified the filter's statistics-based pruning logic to be more accurate, only pruning when the cache indicates a row group is entirely filtered out.

Performance Improvements:

• Optimized the filter function by adding a fast path for flat vectors, reducing overhead in common cases.

Test Adjustments:

• Updated unit tests to construct CacheExpressionFilter with the new CacheKey parameter.

These changes collectively make the query condition cache system more robust, maintainable, and performant.