Add support for `NotebookEdit` in `WorkspaceEdit`

[karthiknadig]

Currently there is no way to provide diffs at the notebook level. We currently receive notebook changes in the form of notebook synchronization events.

The Notebook features that are available from TS APIs like WorkspaceEdit.set is currently not exposed to Language Servers. Having this will allow language servers to perform notebook level "formatting" (restructuring), refactoring, insert/delete/re-order cells.

Adding NotebookEdit support can generally allow updating notebooks via formatting, code action, or any request.

Notes:

• We will need to add NotebookEdit to WorkspaceEdit, and also introduce a NotebookCellData type since the NotebookCell type is not sufficient to create new cells.
• Core WorkspaceEdit API supports NotebookEdit : https://github.com/microsoft/vscode/blob/29e000b1e5c03e7c9a6fccf3e475f0b5a239e4d6/src/vscode-dts/vscode.d.ts#L3967
• NotebookCellData : https://github.com/microsoft/vscode/blob/29e000b1e5c03e7c9a6fccf3e475f0b5a239e4d6/src/vscode-dts/vscode.d.ts#L14869-L14911

ref: microsoft/vscode#204544

[dbaeumer]

How is this currently triggered via the VS Code API_

[karthiknadig]

This currently isn't, I created this issue as a tracking item for getting details down for the protocol side. I will create and attach this to the core issue to trigger this from the VS Code side.

[dbaeumer]

Ok. Thanks!

[karthiknadig]

@dbaeumer : @rebornix and I are looking into this issue for this milestone. LSP work items might show up on this for the next milestone. We are working on figuring out the Core workspace edit API which actually supports notebooks edits, but there are some minor differences in how we handle addition and removal in LSP vs how it is done in the current Notebook API. Once we have that figured out we will create specific items needed from LSP for this task.