Run ss-redir and every UDP relay on the C++ engines

ss-redir's TCP side moves onto the relay engine (per-listener TOS for the
DSCP ports). src/relay/udp replaces udprelay.cpp: sessions keyed by
client address own their upstream socket and live in a fixed LRU,
AEAD-2022 server sessions are shared through RefPtr between the
session-ID table and the relays using them, and datagrams waiting for
DNS sit in pool slots. Packets are received into and built in
relay-owned buffers instead of a 64 KiB allocation per datagram. The
programs no longer call crypto_init(); Method sets up libsodium and the
replay filter.

scripts/no_heap_baseline.txt

@@ -9,16 +9,15 @@ src/crypto.cpp 4
 src/ipset.cpp 3
 src/jconf.cpp 16
 src/json.cpp 2
-src/local.cpp 2
+src/local.cpp 1
 src/manager.cpp 14
 src/plugin.cpp 3
 src/process.cpp 26
-src/redir.cpp 15
+src/redir.cpp 1
 src/rule.cpp 2
 src/server.cpp 4
 src/ss_event.cpp 5
 src/ssurl.cpp 3
 src/stream.cpp 3
-src/tunnel.cpp 2
-src/udprelay.cpp 7
+src/tunnel.cpp 1
 src/utils.cpp 10