cleanup: move bogon checking code in netxlite (#562)

I develop this diff while working on https://github.com/ooni/probe/issues/1803#issuecomment-957323297.

While there, make sure we don't have duplicate bogon code
and always use the code inside netxlite.

internal/measurex/bogon.go

@@ -1,56 +0,0 @@
-package measurex
-
-//
-// Bogon
-//
-// This file helps us to decide if an IPAddr is a bogon.
-//
-
-// TODO(bassosimone): code in engine/netx should use this file.
-
-import (
-	"net"
-
-	"github.com/ooni/probe-cli/v3/internal/runtimex"
-)
-
-// isBogon returns whether if an IP address is bogon. Passing to this
-// function a non-IP address causes it to return true.
-func isBogon(address string) bool {
-	ip := net.ParseIP(address)
-	return ip == nil || isPrivate(ip)
-}
-
-var privateIPBlocks []*net.IPNet
-
-func init() {
-	for _, cidr := range []string{
-		"0.0.0.0/8",      // "This" network (however, Linux...)
-		"10.0.0.0/8",     // RFC1918
-		"100.64.0.0/10",  // Carrier grade NAT
-		"127.0.0.0/8",    // IPv4 loopback
-		"169.254.0.0/16", // RFC3927 link-local
-		"172.16.0.0/12",  // RFC1918
-		"192.168.0.0/16", // RFC1918
-		"224.0.0.0/4",    // Multicast
-		"::1/128",        // IPv6 loopback
-		"fe80::/10",      // IPv6 link-local
-		"fc00::/7",       // IPv6 unique local addr
-	} {
-		_, block, err := net.ParseCIDR(cidr)
-		runtimex.PanicOnError(err, "net.ParseCIDR failed")
-		privateIPBlocks = append(privateIPBlocks, block)
-	}
-}
-
-func isPrivate(ip net.IP) bool {
-	if ip.IsLoopback() || ip.IsLinkLocalUnicast() || ip.IsLinkLocalMulticast() {
-		return true
-	}
-	for _, block := range privateIPBlocks {
-		if block.Contains(ip) {
-			return true
-		}
-	}
-	return false
-}

internal/measurex/resolver.go

@@ -175,7 +175,7 @@ func (r *resolverDB) computeOddityLookupHost(addrs []string, err error) Oddity {
 		}
 	}
 	for _, addr := range addrs {
-		if isBogon(addr) {
+		if netxlite.IsBogon(addr) {
 			return OddityDNSLookupBogon
 		}
 	}