[ENHANCE] Incomplete block cache sharing implementation

Feature Description

The current implementation of share_block_cache is broken:

• No configuration parsing for share-block-cache option
• When share_block_cache=true, no block cache is created (inverted logic)
• Each RocksDB instance creates separate block caches instead of sharing one

When share-block-cache=yes:

• Create a single global block cache shared across all RocksDB instances
• All Column Families use the shared cache instead of individual ones

Motivation

1. Memory efficiency (single shared cache vs multiple individual caches)
2. Better cache hit rates across all instances
3. Proper configuration support

Additional Context

No response