objstorage: Wrap compression operations in utility methods
Wrap object storage backends common code related to compressing an object to store
and decompressing a stored object in utility methods of the base ObjStorage
class
in order to centralize errors handling.
Catch possible exceptions decompressors might raise and raise an
ObjCorruptedError
exception in such cases.
Depend on !178 (merged).
Related to swh-scrubber#4694.
Edited by Antoine Lambert