Fix TF T5/LED missing cross attn in retrun values
# What does this PR do?

Add cross attention to return values for TF T5/LED (so aligned with PT's version).

(Also needed to add a fix of `undoing padding`. Same undoing padding is required for longformer, but it is done in another PR)

@patrickvonplaten 

_The documentation is not available anymore as the PR was closed or merged._<|||||>Great PR - thanks a lot!<|||||>CI failure is unrelated