since w1a2 is coming

unfortunately some bugs in onnxruntime made the previous approach
crash with certain test topologies, so we're opting for this
instead.

dim restriction: mul must be scalar or 1d
val restriction: mul value must be non-negative

[Test] Changed verification method to a check if all tensor shapes are set and the output of the new node has specific value

switched to giving random names first because the old names can
still contain enumerated names