Add saved and executed events to notebook changed (#5848)

- Updated the notebook API to add a change kind, and support saved, executed and other simplified status
- Plumbed this through to the main thread classes
- Support sending the events from cell / input to the notebook model so they loop over the extension host as a content changed event
- Add executed event from the cell

src/vs/workbench/api/browser/mainThreadSaveParticipant.ts

@@ -54,8 +54,8 @@ class NotebookUpdateParticipant implements ISaveParticipantParticipant {
 	}
 
 	public participate(model: ITextFileEditorModel, env: { reason: SaveReason }): Promise<void> {
-		let uriString = model.getResource().toString();
-		let notebookEditor = this.notebookService.listNotebookEditors().find((editor) => editor.id === uriString);
+		let uri = model.getResource();
+		let notebookEditor = this.notebookService.findNotebookEditor(uri);
 		if (notebookEditor) {
 			notebookEditor.notebookParams.input.updateModel();
 		}