ci: move public-api goldens to goldens directory (#35768)

Moves the public api .d.ts files from tools/public_api_guard to
goldens/public-api.

Additionally, provides a README in the goldens directory and a script
assist in testing the current state of the repo against the goldens as
well as a command for accepting all changes to the goldens in a single
command.

PR Close #35768

goldens/public-api/localize/index.d.ts

@@ -0,0 +1,3 @@
+export declare function clearTranslations(): void;
+
+export declare function loadTranslations(translations: Record<MessageId, TargetMessage>): void;