net: only assume all local addresses if listening on any

If `-bind=` is provided then we would bind only to a particular address
and should not add all the other addresses of the machine to the list of
local addresses.

Fixes https://github.com/bitcoin/bitcoin/issues/20184 (case 4.)

src/net.h

@@ -183,7 +183,15 @@ enum class ConnectionType {
 
 /** Convert ConnectionType enum to a string value */
 std::string ConnectionTypeAsString(ConnectionType conn_type);
+
+/**
+ * Look up IP addresses from all interfaces on the machine and add them to the
+ * list of local addresses to self-advertise.
+ * The loopback interface is skipped and only the first address from each
+ * interface is used.
+ */
 void Discover();
+
 uint16_t GetListenPort();
 
 enum