Merge bitcoin/bitcoin#22050: p2p: remove tor v2 support

5d82a57 contrib: remove torv2 seed nodes (Jon Atack)
5f7e086 contrib: update generate-seeds.py to ignore torv2 addresses (Jon Atack)
8be56f0 p2p, refactor: extract OnionToString() from CNetAddr::ToStringIp() (Jon Atack)
5f9d3c0 p2p: remove torv2 from CNetAddr::ToStringIP() (Jon Atack)
3d39042 p2p: remove torv2 in SetIP() and ADDR_TORV2_SIZE constant (Jon Atack)
cff5ec4 p2p: remove pre-addrv2 onions from SerializeV1Array() (Jon Atack)
4192a74 p2p: ignore torv2-in-ipv6 addresses in SetLegacyIPv6() (Jon Atack)
1d631e9 p2p: remove BIP155Network::TORV2 from GetBIP155Network() (Jon Atack)
7d1769b p2p: remove torv2 from SetNetFromBIP155Network() (Jon Atack)
eba9a94 fuzz: rename CNetAddr/CService deserialize targets (Jon Atack)
c56a1c9 p2p: drop onions from IsAddrV1Compatible(), no longer relay torv2 (Jon Atack)
f8e9400 p2p: remove torv2/ADDR_TORV2_SIZE from SetTor() (Jon Atack)
0f1c58a test: update feature_proxy to torv3 (Jon Atack)

Pull request description:

  ![image](https://user-images.githubusercontent.com/2415484/120018909-4d425a00-bfd7-11eb-83c9-95a3dac97926.jpeg)

  This patch removes support in Bitcoin Core for Tor v2 onions, which are already removed from the release of Tor 0.4.6.

  - no longer serialize/deserialize and relay Tor v2 addresses
  - ignore incoming Tor v2 addresses
  - remove Tor v2 addresses from the addrman and peers.dat on node launch
  - update generate-seeds.py to ignore Tor v2 addresses
  - remove Tor v2 hard-coded seeds

  Tested with tor-0.4.6.1-alpha (no v2 support) and 0.4.5.7 (v2 support). With the latest Tor (no v2 support), this removes all the warnings like those reported with current master in bitcoin/bitcoin#21351

  ```
  <bitcoind debug log>
  Socks5() connect to […].onion:8333 failed: general failure

  <tor log>
  Invalid hostname [scrubbed]; rejecting
  ```

  and the addrman no longer has Tor v2 addresses on launching bitcoind.
  ```rake
  $ ./src/bitcoin-cli -addrinfo
  {
    "addresses_known": {
      "ipv4": 44483,
      "ipv6": 8467,
      "torv2": 0,
      "torv3": 2296,
      "i2p": 6,
      "total": 55252
    }
  }
  ```
  After recompiling back to current master and restarting with either of the two Tor versions (0.4.5.7 or 0.4.6.1), -addrinfo initially returns 0 Tor v2 addresses and then begins finding them again.

  Ran nodes on this patch over the past week on mainnet/testnet/signet/regtest after building with DEBUG_ADDRMAN.

  Verified that this patch bootstraps an onlynet=onion node from the Tor v3 hardcoded fixed seeds on mainnet and testnet and connects to blocks and v3 onion peers: `rm ~/.bitcoin/testnet3/peers.dat ; ./src/bitcoind -testnet -dnsseed=0 -onlynet=onion`

  ![Screenshot from 2021-05-28 00-26-17](https://user-images.githubusercontent.com/2415484/119905021-ea02ea00-bf3a-11eb-875f-27ef57640c49.png)

  Tested using `addnode`, `getaddednodeinfo`,`addpeeraddress`, `disconnectnode` and `-addrinfo` that a currently valid, connectable Tor v2 peer can no longer be added:

  ![Screenshot from 2021-05-30 11-32-05](https://user-images.githubusercontent.com/2415484/120099282-29435d80-c12a-11eb-81b6-5084244d7d2a.png)

  Thanks to Vasil Dimov, Carl Dong, and Wladimir J. van der Laan for their work on BIP155 and Tor v3 that got us here.

ACKs for top commit:
  laanwj:
    Code review ACK 5d82a57

Tree-SHA512: 590ff3d2f6ef682608596facb4b01f44fef69716d2ab3552ae1655aa225f4bf104f9ee08d6769abb9982a8031de93340df553279ce1f5023771f9f2b651178bb

Author: laanwj

contrib/seeds/generate-seeds.py

@@ -37,7 +37,7 @@
 class BIP155Network(Enum):
     IPV4 = 1
     IPV6 = 2
-    TORV2 = 3
+    TORV2 = 3  # no longer supported
     TORV3 = 4
     I2P = 5
     CJDNS = 6
@@ -46,11 +46,11 @@ def name_to_bip155(addr):
     '''Convert address string to BIP155 (networkID, addr) tuple.'''
     if addr.endswith('.onion'):
         vchAddr = b32decode(addr[0:-6], True)
-        if len(vchAddr) == 10:
-            return (BIP155Network.TORV2, vchAddr)
-        elif len(vchAddr) == 35:
-            assert(vchAddr[34] == 3)
+        if len(vchAddr) == 35:
+            assert vchAddr[34] == 3
             return (BIP155Network.TORV3, vchAddr[:32])
+        elif len(vchAddr) == 10:
+            return (BIP155Network.TORV2, vchAddr)
         else:
             raise ValueError('Invalid onion %s' % vchAddr)
     elif addr.endswith('.b32.i2p'):
@@ -100,7 +100,10 @@ def parse_spec(s):
 
     host = name_to_bip155(host)
 
-    return host + (port, )
+    if host[0] == BIP155Network.TORV2:
+        return None  # TORV2 is no longer supported, so we ignore it
+    else:
+        return host + (port, )
 
 def ser_compact_size(l):
     r = b""
@@ -136,6 +139,8 @@ def process_nodes(g, f, structname):
             continue
 
         spec = parse_spec(line)
+        if spec is None:  # ignore this entry (e.g. no longer supported addresses like TORV2)
+            continue
         blob = bip155_serialize(spec)
         hoststr = ','.join(('0x%02x' % b) for b in blob)
         g.write(f'    {hoststr},\n')