Allow config_feature_flag usage in OSS starlark rules

Starlark rules can't access `config_common.config_feature_flag_transition`, which pull implicit dependency, `@bazel_tools//tools/allowlits/config_feature_flag_setter`, which doesn't exist. Make its package public otherwise Bazel will throw `the rule class is not allowed access to feature flags setter transition` error.

We don't want new users to use feature_flags in OSS world. We expose this feature for feature parity during migration from native rules to stalark rules, but soon it will be dropped.

PiperOrigin-RevId: 554530156
Change-Id: I5e6b53862d76e608a839897a09701a21ca994a62

tools/allowlists/config_feature_flag/BUILD.tools

@@ -12,3 +12,8 @@ package_group(
     name = "config_feature_flag",
     packages = ["public"],
 )
+
+package_group(
+    name = "config_feature_flag_setter",
+    packages = ["public"],
+)