feat(oohelperd): follow (and record) TH and probe endpoints (#890)

This diff introduces the following `oohelperd` enhancements:

1. measure both IP addresses resolved by the TH and IP addresses resolved by the probe;

2. when the URL scheme is http and there's no explicit port, measure both 80 and 443 (which will pay off big once we introduce support for optionally performing TLS handshakes);

3. include information about the probe and TH IP addresses into the results: who resolved each IP address, whether an address is a bogon, the ASN associated to an address.

This diff is part of https://github.com/ooni/probe/issues/2237

internal/cmd/oohelperd/handler_test.go

@@ -51,7 +51,7 @@ const requestWithoutDomainName = `{
 	]
 }`
 
-func TestWorkingAsIntended(t *testing.T) {
+func TestHandlerWorkingAsIntended(t *testing.T) {
 	handler := &handler{
 		MaxAcceptableBody: 1 << 24,
 		NewClient: func() model.HTTPClient {