fix(p2p): collapse relay circuit dial fan-out and throttle denied dials

[varex83agent]

Closes #564.

Circuit dials bundled one address per (reserved relay x relay transport addr) into a single DialOpts, and libp2p dials every address concurrently — so one campaign fired N simultaneous HOP CONNECT requests per peer pair and exhausted the relay's circuit rate limiter (794 ResourceLimitExceeded denials in ~10 min on hoodi, all nodes at 0 peers). A relay's transport addrs are alternative routes to the relay, not to the target, and rust-libp2p's circuit client reuses the already-open relay connection (priv_client::Behaviour DialReq handling), so the dial side is now collapsed to exactly one circuit address per reserved relay — mirroring what the reservation/listener side already does.

Denials are now also acted on: RelayDialError gains a ResourceLimitExceeded variant, classified by walking the source() chain of the boxed transport error (every intermediate Display drops its source, so the raw message was a useless "Failed to connect to destination."), and a denied campaign is parked for at least 30s via RelayDialState::throttle_denied instead of restarting the 1s ladder. Finally, upsert_peer_dial now swaps the address set in place rather than rebuilding the dial state, so a flapping relay no longer resets retry_count to zero on every Reserved transition and pins the campaign to the base delay forever.

Co-Authored-By: Bohdan Ohorodnii 35969035+varex83@users.noreply.github.com