Sidecar mode doesn't resize the jdaviz height when it's moved around

[eteq]

If I open up a jdaviz (for the illustration below I used imviz but I see the same on other viz'es) instance from jupyterlab using .show('sidecar:...'), it pops up just fine in the expected place, but if I move the window around, it doesn't resize the height, so there ends up being a lot of wasted whitespace - see the screenshots below. I can work-around this for now by doing .show('sidecar:...', height=the_size_of_the_browser_window) but that's not idea if I re-arrange my jupyterlab workspace.

The screenshots below come from showing an imviz window as .show('sidcar:tab-after') and then dragging it first down below the notebook, and then off to the right. In both cases the width correctly updates but the height does not

[eteq]

This might be fixed by #1788 but I haven't gotten that PR to work to test it.