Merge bitcoin/bitcoin#20234: net: don't bind on 0.0.0.0 if binds are restricted to Tor

2feec3ce31 net: don't bind on 0.0.0.0 if binds are restricted to Tor (Vasil Dimov)

Pull request description:

  The semantic of `-bind` is to restrict the binding only to some address.
  If not specified, then the user does not care and we bind to `0.0.0.0`.
  If specified then we should honor the restriction and bind only to the
  specified address.

  Before this change, if no `-bind` is given then we would bind to
  `0.0.0.0:8333` and to `127.0.0.1:8334` (incoming Tor) which is ok -
  the user does not care to restrict the binding.

  However, if only `-bind=addr:port=onion` is given (without ordinary
  `-bind=`) then we would bind to `addr:port` _and_ to `0.0.0.0:8333` in
  addition.

  Change the above to not do the additional bind: if only
  `-bind=addr:port=onion` is given (without ordinary `-bind=`) then bind
  to `addr:port` (only) and consider incoming connections to that as Tor
  and do not advertise it. I.e. a Tor-only node.

ACKs for top commit:
  laanwj:
    Code review ACK 2feec3ce31
  jonatack:
    utACK 2feec3ce31 per `git diff a004833 2feec3c`
  hebasto:
    ACK 2feec3ce31, tested on Linux Mint 20.1 (x86_64):

Tree-SHA512: a04483af601706da928958b92dc560f9cfcc78ab0bb9d74414636eed1c6f29ed538ce1fb5a17d41ed82c9c9a45ca94899d0966e7ef93da809c9bcdcdb1d1f040

test/functional/test_runner.py

@@ -139,6 +139,7 @@ BASE_SCRIPTS = [
     'interface_zmq.py',
     'rpc_invalid_address_message.py',
     'interface_bitcoin_cli.py',
+    'feature_bind_extra.py',
     'mempool_resurrect.py',
     'wallet_txn_doublespend.py --mineblock',
     'tool_wallet.py --legacy-wallet',