Feat/notebooks viewlet (#10170)

* clean up unsavedBooks to providedBooks

* added notebooks viewley contribution

* added notebookExporerAction context

* temp shortcut key B

* remove commenred code

* changes with master merge

* fix comments

* initial tests

* fix casing and description

* merged master and resolved errors

* remove extension point & add custom view container

* merge latest from master

* remove unused files

* move book images to common

* remove notebookExplorer contrib & move to notebook

* build fix

* remove explorer specific sryles from common

* vscode convention to define container actions

* rename notebooks/title

src/sql/workbench/contrib/notebook/browser/media/notebook.contribution.css

@@ -0,0 +1,14 @@
+/*---------------------------------------------------------------------------------------------
+ *  Copyright (c) Microsoft Corporation. All rights reserved.
+ *  Licensed under the Source EULA. See License.txt in the project root for license information.
+ *--------------------------------------------------------------------------------------------*/
+
+/* Activity Bar */
+.monaco-workbench .activitybar .monaco-action-bar .action-label.book {
+	background-color: rgba(255, 255, 255, 0.4);
+}
+
+/* Activity Bar */
+.monaco-workbench .activitybar .monaco-action-bar .checked .action-label.book {
+	background-color: rgb(255, 255, 255);
+}