Add custom ice stdnet implementation (#754)

On Android, because of the hard SELinux policies can not list the
interfaces of the ICE package. Without it can not generate a host type
candidate. In this pull request, the list of interfaces comes via the Java
interface.

client/internal/stdnet/stdnet_test.go

@@ -0,0 +1,52 @@
+package stdnet
+
+import (
+	"fmt"
+	"testing"
+)
+
+func Test_parseInterfacesString(t *testing.T) {
+	testData := []struct {
+		name         string
+		index        int
+		mtu          int
+		up           bool
+		broadcast    bool
+		loopBack     bool
+		pointToPoint bool
+		multicast    bool
+		addr         string
+	}{
+		{"wlan0", 30, 1500, true, true, false, false, true, "10.1.10.131/24"},
+		{"rmnet0", 30, 1500, true, true, false, false, true, "192.168.0.56/24"},
+	}
+
+	var exampleString string
+	for _, d := range testData {
+		exampleString = fmt.Sprintf("%s\n%s %d %d %t %t %t %t %t | %s", exampleString,
+			d.name,
+			d.index,
+			d.mtu,
+			d.up,
+			d.broadcast,
+			d.loopBack,
+			d.pointToPoint,
+			d.multicast,
+			d.addr)
+	}
+	nets := parseInterfacesString(exampleString)
+	if len(nets) == 0 {
+		t.Fatalf("failed to parse interfaces")
+	}
+
+	for i, net := range nets {
+		if net.MTU != testData[i].mtu {
+			t.Errorf("invalid mtu: %d, expected: %d", net.MTU, testData[0].mtu)
+
+		}
+
+		if net.Interface.Name != testData[i].name {
+			t.Errorf("invalid interface name: %s, expected: %s", net.Interface.Name, testData[i].name)
+		}
+	}
+}