[mlir][Tensor] Fix unpack -> transpose folding pattern for padded unpacks (#90678)

Previously if the producer tensor.unpack op had "unpadding" semantics,
the folding pattern would construct a destination that does not match
with the result type of the transpose. Because both ops are DPS we can
just reuse the destination of the transpose.

Additionally cleans up a bunch of trailing whitespace in the test file.