feat: add FileStore implementation for cache (#427)

[achsanalfitra]

Pull Request to Issue #427

Key info:

• CAS-based registry
• Hashed using md-5 (which is already an existing dependency from sqlx)
• Eviction on get and contains key (similar to memory cache)

Note:

• Uses DateTime to parse serialized expiry into Timeout (this can be improved by implementing From in Timeout)
• No retry policy implemented
• No entry cap implemented