Introduce shared Store drivers and refactor Session/Cache/Throttle to use them

[ismailian]

Motivation

• Reduce duplication by extracting generic storage primitives that can be reused by Session, Cache and Throttle layers.
• Keep backend implementations (filesystem, Redis, database) centralized and driver-agnostic so each core (Session/Cache/Throttle) only contains behaviour specific to its responsibilities.
• Allow adding new backends (e.g. DB-backed cache) without duplicating storage logic across subsystems.

Description

• Added a new shared driver layer under System/Drivers with a generic StoreDriver contract and implementations: FilesystemDriver, RedisDriver, and DatabaseDriver which expose getAll, get, set, delete, increment, and ttl APIs.
• Refactored Session drivers (System/Session/Drivers/{FileDriver,RedisDriver,DbDriver}) to delegate storage to the shared store drivers while preserving session-facing methods (read, write, delete, getAll).
• Refactored Cache drivers to use the shared drivers and added System/Cache/Drivers/DbDriver, and updated System/Cache/Cache.php to support DataSource::DATABASE in the init() driver selection.
• Refactored Throttle drivers to delegate counters/TTL semantics to the shared drivers and implemented the RateLimiterDriver adapters (FilesystemDriver, RedisDriver, DatabaseDriver) to expose get, increment, ttl, and reset while keeping rate-limit logic in RateLimiter.

Testing

• Ran PHP lint across the new/modified files using php -l for System/Drivers/*, System/Session/Drivers/*, System/Cache/*, and System/Throttle/Drivers/*, and all files reported No syntax errors detected.
• No automated unit tests were present; validation was limited to the syntax/lint checks which succeeded.

---

Codex Task