feat: introduce block meta cache

[dantengsky]

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Summary

We previously had a block meta cache, but it was rather coarse-grained. Blockmetas were cached at the segment level, which worked reasonably for scenarios like general table pruning. However, for operations like replace into, we needed something more fine-grained.

So, in this PR:

• Rename the old segment-level block meta cache to SegmentBlockMetasCache.
  Each item in this cache is an array of BlockMeta objects, representing all the block metas for a specific segment.

• Introduce a new BlockMetaCache.
  Each item in this cache is a single BlockMeta.

• Adjust system.caches and system$set_cache_capacity to fit these changes.

Tests

• Unit Test
• Logic Test
• Benchmark Test
• No Test - Explain why

Type of change

• Bug Fix (non-breaking change which fixes an issue)
• New Feature (non-breaking change which adds functionality)
• Breaking Change (fix or feature that could cause existing functionality not to work as expected)
• Documentation Update
• Refactoring
• Performance Improvement
• Other (please describe):

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