Optionally get rid of intermediary boxes in visualize, and add more labels

[jsignell]

• Tests added / passed
• Passes black dask / flake8 dask

This PR adds the collapse and verbose options to visualize. Collapse gets rid of all non-connected non-task boxes as well as any boxes that are just the output of a task that feeds into other tasks. Verbose adds a label to all the boxes even if the label is a duplicate.

This came up in #5928. Here are some images of what the new graphs from that page would look like:

With lots of intermediary outputs

	collapse=False	collapse=True
verbose=False
verbose=True

With unconnected nodes

	collapse=False	collapse=True
verbose=False
verbose=True

[jsignell]

@quasiben since we were talking about this at the dask meeting.

[TomAugspurger]

Thanks, this looks really nice.

Do you have an example of collapse removing an unconnected box? Or is it in the examples you posted and I just missed it?

[TomAugspurger]

CI failure is just #5972, which I haven't had any luck with yet.

[jsignell]

I added an unconnected nodes example to the first comment.

[TomAugspurger]

Great, thanks.

I pushed a commit merging master, which should make the CI failure go away.

[TomAugspurger]

Merging later today if there aren't any objections.

[jsignell]

Thanks!

[jsignell]

I'll redo #5928 once this is in :)

[jrbourbeau]

Thanks @jsignell!