Query Cache | GTID based cache consistency

As a user, I want the MaxScale Cache Filter to track cache freshness using per-table GTID state, so that cached results are invalidated the moment underlying data changes — not just after a TTL window expires.

Proposed approach (for discussion):

• Maintain a tracking table (in-memory or master table) that records the last GTID at which each table had a DML operation (insert/update/delete/alter).
• Tag each cached query result with the GTID at the time it was generated.
• On cache read, compare the cached result's GTID against the tracking table's latest GTID for the tables involved. If the tracking table is ahead, the entry is stale.
• On a stale hit, fall through to the backend, fetch fresh data, and re-cache with the new GTID.

This should be built as a common capability in the Cache Filter, so any storage backend gets write-triggered invalidation and read-after-write consistency