[CLEANUP] Clean up comments and error messages in ResourceStorage

This changes adds some missing @throws annotations and improves the
readability of some comments.

Also fix a typo in an exception and reformat some exceptions for
better readability.

Moreover add some checks if the correct type is present
before calling undefined methods.

This change does not introduce any functional changes.

Releases: 6.2
Resolves: #57871
Change-Id: Iab4414bd480a05cc5ca3b29df0d12e719064b063
Reviewed-on: https://review.typo3.org/29439
Reviewed-by: Markus Klein
Tested-by: Markus Klein
Reviewed-by: Stefan Neufeind
Tested-by: Stefan Neufeind