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/ui/build/upload.go b/ui/build/upload.go
index 55ca800..55ada33 100644
--- a/ui/build/upload.go
+++ b/ui/build/upload.go
@@ -24,7 +24,8 @@
 	"time"
 
 	"android/soong/ui/metrics"
-	"github.com/golang/protobuf/proto"
+
+	"google.golang.org/protobuf/proto"
 
 	upload_proto "android/soong/ui/metrics/upload_proto"
 )