Make protocOpts() public. (bazelbuild#14952)

* Make protocOpts() public.

RELNOTES:
Make protocOpts() publicly accessible.
PiperOrigin-RevId: 430726712

* Cleanup

* Add import.

* Add the right import.

Co-authored-by: Googler <[email protected]>

Author: comius

src/main/java/com/google/devtools/build/lib/rules/proto/BUILD

@@ -51,6 +51,7 @@ java_library(
         "//src/main/java/com/google/devtools/build/lib/vfs",
         "//src/main/java/com/google/devtools/build/lib/vfs:pathfragment",
         "//src/main/java/com/google/devtools/common/options",
+        "//src/main/java/net/starlark/java/annot",
         "//src/main/java/net/starlark/java/eval",
         "//third_party:auto_value",
         "//third_party:guava",

src/main/java/com/google/devtools/build/lib/rules/proto/ProtoConfiguration.java

@@ -30,6 +30,7 @@
 import com.google.devtools.common.options.OptionEffectTag;
 import com.google.devtools.common.options.OptionMetadataTag;
 import java.util.List;
+import net.starlark.java.annot.StarlarkMethod;
 
 /** Configuration for Protocol Buffer Libraries. */
 @Immutable
@@ -201,6 +202,7 @@ public ProtoConfiguration(BuildOptions buildOptions) {
     this.options = options;
   }
 
+  @StarlarkMethod(name = "experimental_protoc_opts", structField = true, documented = false)
   public ImmutableList<String> protocOpts() {
     return protocOpts;
   }