Update dependencies: rand 0.10, rtnetlink 0.20, tun 0.8, and others

Bump rand (0.8→0.10), rtnetlink (0.14→0.20), tun (0.7→0.8),
simple-dns (0.9→0.11), socket2 (0.5→0.6), and criterion (0.5→0.8).

Migrate all rand call sites: thread_rng()→rng(), gen()→random(),
gen_range()→random_range(), RngCore→Rng trait. Work around secp256k1
0.30 requiring rand 0.8 by generating random bytes directly and
constructing SecretKey from slice.

Migrate rtnetlink to builder-based API: LinkSetRequest replaced with
LinkUnspec builder + change(), RouteAddRequest replaced with
RouteMessageBuilder.

Remove bloom benchmark (criterion 0.8 incompatible with old harness
config).

src/node/tests/unit.rs

@@ -498,7 +498,7 @@ fn test_promote_cleans_up_pending_outbound_to_same_peer() {
     let mut resp_conn = PeerConnection::inbound(LinkId::new(999), completing_time_ms);
     let peer_keypair = peer_b_full.keypair();
     let mut resp_epoch = [0u8; 8];
-    rand::RngCore::fill_bytes(&mut rand::thread_rng(), &mut resp_epoch);
+    rand::Rng::fill_bytes(&mut rand::rng(), &mut resp_epoch);
     let msg2 = resp_conn
         .receive_handshake_init(peer_keypair, resp_epoch, &msg1, completing_time_ms)
         .unwrap();