Take the Tor exit list from Onionoo, which has the IPv6 exits (closes #234)

`check.torproject.org` lists IPv4 exits only, so `is_tor` was false for an IPv6 exit. `tor_exits` now comes from Onionoo through a new format that reads `relays[].exit_addresses` and `relays[].or_addresses`. IPv6 addresses come only from `or_addresses`, the address a relay accepts Tor connections on, so an exit leaving from another IPv6 address still has `is_tor` false.

Judgement call: a document with no addresses fails the parse.
Rule suppressed: `tagliatelle` on the struct holding Onionoo's field names.

Model: opus-5-5

internal/iplist/iplist.go

@@ -29,6 +29,11 @@ const (
 	// start with the network's first and last address. Lines that start
 	// with # are comments.
 	FormatDShield
+
+	// FormatOnionooJSON is one Onionoo details document. Its relays have
+	// addresses in two fields: exit_addresses, which has IPv4 only, and
+	// or_addresses, which has IPv4 and IPv6, each with a port.
+	FormatOnionooJSON
 )
 
 // List is one public IP list.