Upgrade to golang protobuf api v2

Major operations:
 * Fix the go_package entries to be consistent, as the new tool
   complains when it doesn't have a '/'.
 * Regenerate with the new protoc-gen-go tool.
 * github.com/golang/protobuf -> google.golang.org/protobuf
 * proto.[Un]MarshalText -> prototext.[Un]Marshal

Change-Id: Ie1147bd2457fafb66ba555461b3bf14f0561a25d
diff --git a/cmd/extract_apks/main.go b/cmd/extract_apks/main.go
index db54ffb..6e51a28 100644
--- a/cmd/extract_apks/main.go
+++ b/cmd/extract_apks/main.go
@@ -27,9 +27,9 @@
 	"sort"
 	"strings"
 
-	"github.com/golang/protobuf/proto"
+	"google.golang.org/protobuf/proto"
 
-	"android/soong/cmd/extract_apks/bundle_proto"
+	android_bundle_proto "android/soong/cmd/extract_apks/bundle_proto"
 	"android/soong/third_party/zip"
 )