[perl #27010] Make tie work through defelems

When elements of @_ refer to nonexistent hash or array elements, then
the magic scalar in $_[0] delegates all set/get actions to the element
in represents, vivifying it if needed.

tie/tied/untie, however, were not delegating to the element, but were
tying the the magical ‘deferred element’ scalar itself.
perldelta for #27010