netxlite: call getaddrinfo and handle platform-specific oddities (#764)

This commit changes our system resolver to call getaddrinfo directly when CGO is enabled. This change allows us to:

1. obtain the CNAME easily

2. obtain the real getaddrinfo retval

3. handle platform specific oddities such as `EAI_NODATA`
returned on Android devices

See https://github.com/ooni/probe/issues/2029 and https://github.com/ooni/probe/issues/2029#issuecomment-1140258729 in particular.

See https://github.com/ooni/probe/issues/2033 for documentation regarding the desire to see `getaddrinfo`'s retval.

See https://github.com/ooni/probe/issues/2118 for possible follow-up changes.

internal/engine/experiment/sniblocking/sniblocking.go

@@ -68,7 +68,7 @@ func (tk *TestKeys) classify() string {
 		return classAnomalyTestHelperUnreachable
 	case netxlite.FailureConnectionReset:
 		return classInterferenceReset
-	case netxlite.FailureDNSNXDOMAINError:
+	case netxlite.FailureDNSNXDOMAINError, netxlite.FailureAndroidDNSCacheNoData:
 		return classAnomalyTestHelperUnreachable
 	case netxlite.FailureEOFError:
 		return classInterferenceClosed

internal/engine/experiment/sniblocking/sniblocking_test.go

@@ -12,11 +12,6 @@ import (
 	"github.com/ooni/probe-cli/v3/internal/netxlite"
 )
 
-const (
-	softwareName    = "ooniprobe-example"
-	softwareVersion = "0.0.1"
-)
-
 func TestTestKeysClassify(t *testing.T) {
 	asStringPtr := func(s string) *string {
 		return &s
@@ -41,6 +36,13 @@ func TestTestKeysClassify(t *testing.T) {
 			t.Fatal("unexpected result")
 		}
 	})
+	t.Run("with tk.Target.Failure == android_dns_cache_no_data", func(t *testing.T) {
+		tk := new(TestKeys)
+		tk.Target.Failure = asStringPtr(netxlite.FailureAndroidDNSCacheNoData)
+		if tk.classify() != classAnomalyTestHelperUnreachable {
+			t.Fatal("unexpected result")
+		}
+	})
 	t.Run("with tk.Target.Failure == connection_reset", func(t *testing.T) {
 		tk := new(TestKeys)
 		tk.Target.Failure = asStringPtr(netxlite.FailureConnectionReset)