global: replace most uses of RevlogError with StorageError (API) When catching errors in storage, we should be catching StorageError instead of RevlogError. When throwing errors related to storage, we shouldn't be using RevlogError unless we know the error stemmed from revlogs. And we only reliably know that if we're in revlog.py or are inheriting from a type defined in revlog.py. Differential Revision: https://phab.mercurial-scm.org/D4655