Optimize INFORMATION_SCHEMA Queries (MDEV-31342 & MDEV-31535)

This project aims to resolve significant performance bottlenecks in MariaDB’s INFORMATION_SCHEMA when dealing with a high number of databases or tables. Currently, many INFORMATION_SCHEMA queries require the creation of internal temporary tables and expensive filesystem scans. The proposal focuses on two major optimizations: MDEV-31342: Implementing a mechanism to bypass temporary table creation for simple queries, allowing results to be streamed directly to the client. MDEV-31535: Optimizing the directory scanning process by leveraging the in-memory privilege cache to filter database/table visibility, thereby reducing redundant and slow I/O operations. Combined, these changes will drastically improve the responsiveness of metadata queries in large-scale MariaDB deployments.