BUG: ipympl not properly tested on Windows

[larsoner]

So the difference that is causing the failed tests is that pympl was not installed by conda. Without it, the plots don't actually show up in notebook so I think it should be added as a dependency we should figure out how to get all the failed tests on Windows to pass. It appears to have to do with things not having the focus and therefore not receiving clicks. I might have some time to work on this, but if anyone else wants, especially who wrote those parts, please do jump in. Here are the failed tests: https://dev.azure.com/mne-tools/mne-python/_build/results?buildId=20791&view=logs&j=dded70eb-633c-5c42-e995-a7f8d1f99d91&t=8394206f-a00b-5cb7-44ca-464c9d5f9e25, they're mostly in plot_3d.py and indirectly through things like topomaps.

Originally posted by @alexrockhill in https://github.com/mne-tools/mne-python/issues/10913#issuecomment-1194422527