Ensure that:
* Storage config might be removed.
* Local FS GC process is set up when Local FS storage is configured.
* Local FS GC process gets its timer reset on config updates.
* Storage / exporter gets chosen based on `type` only.
* Exporter config updates propagated as before.
Also employ `emqx_ft_schema:translate/1` instead of duplicating
defaults where applicable.