Make the reflections cache work with strings as its keys.
No need to call `to_sym` on reflection name, since the cache now works
with strings with string keys.

Related #14668.
Make the aggregate_reflections cache work with strings as its keys.
Make sure the reflection test is passing a String to the reflection
cache.
Merge pull request #14675 from laurocaetano/make_reflection_caches_works_with_string_keys

Make reflection and aggregate_reflection caches work with string keys.