Implement interactive window with VS code notebook API

TODO

• #6465
• #6462
• #6421
• #6424
• #6449
• #6456
• #6458
• #4257
• #6457
• #6418

This epic is switching the interactive window to use the VS code notebook API instead of our custom webview.

Here’s a brief list of the requirements (in mostly priority order):

1. Support input from an external source (like a python file)` (already supported)
2. Show all cell outputs in a big read only list (already supported)
3. Support direct input from a text editor that doesn’t move. (vscode upstream)
4. Support hiding/collapsing code in cells (vscode upstream - possibly part of Jupyter Outline) – supported with notebook.cell.collapseCellInput command
5. Support copying code out of cells with some gesture (extension)
6. Support a history of text entered in the pinned text editor (extension)
7. Support theming (already supported)
8. Support intellisense (extension)
9. Support all cell outputs that a notebook does (already supported)
10. Support restarting/interrrupting kernel
11. Support variables
12. Scroll as new inputs come in (behave like chat window) (vscode upstream) – supported with notebook focus commands:

[greazer]

This is done, other than a couple bug stragglers.

[rchiodo]

Same way it works now. The chrome around cells and the toolbar might be different, but it will have the same basic functionality. That’s what the list of requirements at the top are for - to make sure we don’t regress anything that already works.