geolocate: add cloudflare-based IP lookup (#676)

Cloudflare hosted services provide a certain service of `/cdn-cgi/trace` with their base url (for example, `www.cloudflare.com` or `www.nginx.com`), which can be used to obtain `ip` in the probe's `geolocate` feature.

The same feature was added in this pr, hence, increasing the number of `baseURL`s in `geolocate`.

Co-authored-by: Simone Basso <bassosimone@gmail.com>

internal/engine/geolocate/iplookup.go

@@ -40,6 +40,10 @@ var (
 			name: "avast",
 			fn:   avastIPLookup,
 		},
+		{
+			name: "cloudflare",
+			fn:   cloudflareIPLookup,
+		},
 		{
 			name: "ipconfig",
 			fn:   ipConfigIPLookup,