Missing retry in storage and firestore trigger decorators

Hi there,

There doesn't seem to be a way to enable retry on Firebase Storage `storage_fn` and Firestore `firestore_fn` background functions. It would really be helpful if we can enable it similar to the `pubsub_fn.on_message_published(retry=)`.

Start by reading pubsub_fn.on_message_published(retry=) and comparing it with the storage_fn and firestore_fn decorators. Trace the relevant decorator entry points and tests, then verify that both decorators accept retry configuration and that the resulting functions retry as expected.

Written by the indexing model from the issue text.