Add client_routes module for Private Link support

Implement the core client routes module that handles dynamic address
translation via the system.client_routes table. This includes:
 - ClientRouteProxy and ClientRoutesConfig for user-facing configuration
 - _Route dataclass and _RouteStore for records storage
 - _ClientRoutesHandler for route lifecycle management: initialization,
   CLIENT_ROUTES_CHANGE event handling, control connection reconnect,
   querying system.client_routes, and DNS resolution with caching
 - Preferred route selection logic that avoids unnecessary connection_id
   migration when multiple routes exist for the same host

cr

Author: sylwiaszunejko