Introduce "bazel help flags-as-proto" to print information about supported flags as a text protobuf.

PiperOrigin-RevId: 168695297
diff --git a/src/main/protobuf/BUILD b/src/main/protobuf/BUILD
index d20eff5..a9ccaec 100644
--- a/src/main/protobuf/BUILD
+++ b/src/main/protobuf/BUILD
@@ -9,6 +9,7 @@
     "action_cache",
     "android_deploy_info",
     "apk_manifest",
+    "bazel_flags",
     "build",
     "bundlemerge",
     "command_server",