Finalize NotebookEditor api proposal

[mjbvz]

Fixes #149271

This finalizes most parts of the NotebookEditor api proposal. I haven't removed the proposal entirely as there are still a few parts being left behind:

• The deprecated properties/functions
• A few contribution points such as notebook/cell/executePrimary

[mjbvz]

@rebornix and @jrieken I just realized that the notebookEditor proposal is also used to gate the following menu contributions:

• notebook/cell/executePrimary
• interactive/toolbar
• interactive/cell/title

Let me know if these can also be finalized or should be split into a new proposal

[jrieken]

notebook/cell/executePrimary sounds a bit exotic. May this should be notebook/cell/execute with a special group (of length 1) which is rendered prominent. /cc @roblourens for background

[jrieken]

Also debug/toolBar vs notebook/toolbar vs interactive/toolbar (only the latter isn't finalized)

[roblourens]

That executePrimary menu is only needed for remotehub's "Continue Working On" prompt and it will go away when that moves to core. #149271 (comment) I think that menu shouldn't be finalized. Sorry for not calling that out.

[mjbvz]

I've confirmed that interactive/cell/title and interactive/toolbar are being used by the Jupyter extension: https://github.com/microsoft/vscode-jupyter/blob/584e7e126dc1d218909e8277a6e2bb3d65315892/package.json#L1009

Not sure if there are any other users. @roblourens Do you think we can safely finalize these two contributions? Or do they need to remain proposed

[rebornix]

@mjbvz I think both interactive/cell/title and interactive/toolbar are stable and good for finalization. They are similar to notebook/cell/title and notebook/toolbar and they are used uniquely in Interactive Window.