Variable view is not redrawn when moved to a different panel

[joyceerhl]

Originally reported by @thor4 in microsoft/vscode-jupyter#6993 (comment)

1. Create a notebook
2. Run a cell which defines a variable
3. Variable shows up in the Jupyter: Variables view
4. Right click on the Jupyter: Variables title
5. Select 'Move Panel Right'
6. 🐛 variable view UI never reappears

[IanMatthewHuff]

It's interesting. The variable view can be dragged from bottom to sidebar just fine. It gets a dispose and then recreated. But when that entire panel is moved it doesn't get a visibility change, or a dispose or anything like that which I can see. I might actually try to repro this with a super simple example and see if there is a similar issue.

[IanMatthewHuff]

I can actually repro this with the vscode webview-view sample.

The Calico Colors control also disappears when you move the panel. Oddly enough, just looking deeper now, there seems to be some sort of "welcome-view" element that seems to have replaced it?

[IanMatthewHuff]

Repro is just the same basic steps as initially listed using webview-view sample. I dragged the Calico Colors control from the sidebar into the bottom panel (still worked). Then I used Move Panel Right on the bottom set of panels. The control was gone and didn't come back for me.