Replace `core/container.ErrNotFound` error returned by `Source.Get`
interface method with `apistatus.ContainerNotFound` status error. This
error is returned by storage node's server as NeoFS API statuses.
Signed-off-by: Leonard Lyubich <leonard@nspcc.ru>
ErrEACLNotFound error was defined in implementation package. EACL validator
checked this error after the call of eACL storage interface method. Replace
ErrEACLNotFound to core container library. in order to: on the one hand not
use an implementation error, on the other hand, to be able to reuse a
generic type error (404).
Signed-off-by: Leonard Lyubich <leonard@nspcc.ru>
