Books/navigation (#6280)

* added previous and next buttons

* previous and next notebook API

* links for prev/next notebooks

* fixed first and last pages

* made code more readable

* addressed Kevin's comments

* moved logic over to BookTreeItem

* show buttons in dev mode only

* added BookTreeItemFormat interface

* added interface and enum

* removed localize call

src/sql/workbench/api/node/sqlExtHost.api.impl.ts

@@ -501,6 +501,9 @@ export function createApiFactory(
 				registerNotebookProvider(provider: azdata.nb.NotebookProvider): vscode.Disposable {
 					return extHostNotebook.registerNotebookProvider(provider);
 				},
+				registerNavigationProvider(provider: azdata.nb.NavigationProvider): vscode.Disposable {
+					return extHostNotebookDocumentsAndEditors.registerNavigationProvider(provider);
+				},
 				CellRange: sqlExtHostTypes.CellRange,
 				NotebookChangeKind: sqlExtHostTypes.NotebookChangeKind
 			};