Add support for `NotebookEdit` in `WorkspaceEdit`

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: https://github.com/microsoft/vscode/issues/204544

Start by comparing the linked VS Code WorkspaceEdit and NotebookCellData API definitions, then trace the corresponding WorkspaceEdit types in this repository. Done means Language Servers can represent NotebookEdit changes and create new notebook cells through the exposed API, with behavior aligned to the referenced core API.