…o model nodes (#16320)

Signed-off-by: bigcat88 <bigcat88@icloud.com>

Start Loop took the first delivered value of `initial_iteration_value` and
LoopIteration took the first value of `current_iteration_value`, so a Create
List holding mixed state reached the loop body with only its first item. Get
Item From List then raised `IndexError` for every index past 0, which is the
opposite of what the generic loop advertises: one carried value holding an
image and its prompt, unpacked inside the iteration.

Pass the opener's own input into the expanded graph so the first iteration
receives the carried value through the same link the later ones use, and let
LoopIteration re-emit it whole.

…t (CORE-440) (#16333)