refactor(networking): use workspace bootstrap_cache crate

Remove custom bootstrap cache implementation from sn_networking in favor of using
the existing bootstrap_cache crate from the workspace. This change:

* Removes duplicate bootstrap cache implementation from sn_networking
* Updates NetworkDiscovery to use the official bootstrap_cache types
* Ensures consistent cache behavior across sn_node and autonomi through sn_networking
* Manually implements Debug for NetworkDiscovery to handle CacheStore

This change reduces code duplication and ensures consistent bootstrap cache
behavior across the entire codebase.