networkd: Fix race condition in [RoutingPolicyRule] handling (#7615)

networkd: Fix race condition in [RoutingPolicyRule] handling (#7615)

The routing policy rule setup logic is moved to the routes setup phase (rather than the addresses setup phase as it is now). Additionally, a call to `link_check_ready` is added to the routing policy rules setup handler. This prevents a race condition with the routes setup handler.

Also give each async handler its own message counter to prevent race conditions when logging successes.

Fixes: #7614