Cleanup

Tests fix, pydotprint and Better error message.

Also, for the other parameter use float32 to use different dtype.

Also, with int32, make sure to draw the random value correctly. We where drawing only 0s.

Fix gh-2108

Older version of pydot, Edge was accepting the parameter label=''. Now
this cause bug.

Now only the legacy opt move to the GPU. Then we can apply opt in
order to get the behavior we want.

Doc, error message

Update to be more consistent with doc.

Fix gh-2210, Join.grad crash with first input dtype being *int*

Documentation : error messages

Try to clarify

Typo + clarification