The ticket should handle the lifecycle of page cache hashtable, including:
1. Define page cache hashtable and page cache item struct.
2. __wti_page_cache_init, hash table intialization on connection open.
3. __wti_page_cache_destroy, hash table destruction on connection close.

The current POC has completed most of the code, this ticket is to cherry pick or copy the code snippet from the POC branch, then clean up the code, add necessary logging and failing messages.