This catches bugs early on. E.g., when leaving an 'Allocation'
unused, it gets immediately deallocated, which is most probably not
intended. For regular 'Attempt' objects, this change encourages
the proper propagation of errors, or at least the logging of unexpected
conditions.
Fixes#5513
The new variant combines the attempt with unique-pointer semantics
and is thereby usable for returning non-copyable objects such as
RAM 'Allocation'.
Issue #5502
