Change the scope of getMediaTypes method to public
- Change getMediaTypes() visibility to public so it can be reused from other services and plugins.
- Replace all getDamMediaTypes() call sites with getMediaTypes().
- Remove getDamMediaTypes() from AssetUpdater per issue AC #3.
- Fix latent cross-instance cache leak: replace function-scoped static cache with an instance property so the newly-public method has correct per-instance semantics and empty results cache correctly.
- Remove unused ManagedImageField import from MediaTypeResolver.
Issue #3561028: Scope of the getMediaTypes to be public
Closes #3561028