translations: translate "processing.." strings coming from storage

[matejcik]

storage.c has a bunch of baked-in English strings for progress labels. these need to be translated too.

(similar case may be for wipe code erasure and similar)

the way to go seems to be to return an enum instead of literal string, and let the UI code convert to a string.

this can be done after #3206 is merged, to not block it anymore