ENH: Improve report plotting and animate_topomap

[larsoner]

I don't like how long it takes to generate reports, so I was trying to speed it up a bit. In doing so, I realized animate_topomap wasn't working properly, and refactored it to reuse plot_evoked_topomap code. This makes it more feature-complete, and I fixed its behavior (with both blit=True and blit=False). I also made it so the report now has butterfly=True from the animate_topomap, which I think is nice. From this testing code:

MWE

import mne

sample_dir = mne.datasets.sample.data_path() / "MEG" / "sample"
evoked_path = sample_dir / "sample_audvis-ave.fif"
cov_path = sample_dir / "sample_audvis-cov.fif"

evokeds = mne.read_evokeds(evoked_path, baseline=(None, 0))
#fig, anim = evokeds[0].animate_topomap(butterfly=True, frame_rate=2)
report = mne.Report()
report.add_evokeds(
    evokeds=evokeds[:1],
    n_time_points=20,
)
report.save("report_evoked.html", overwrite=True, open_browser=True)

You can see it:

I expect some test breakages, will push fixes for those.