[AutoDiff] Fix `destructure_tuple` differentiation. (#28281)
Fix adjoint accumulation in `PullbackEmitter::destructure_tuple` for tuple
values with non-tuple-typed adjoint values. This is relevant for array literal
initialization because `array.uninitialized_intrinsic` returns a tuple with a
non-tuple-typed adjoint value and a `destructure_tuple` user.
Resolves TF-922.
