Nb/show notebooks as untitled (#6376)

* open notebooks as untitled files and removed the saving to home directory

* return just filename without extension since save is adding the .ipynb ext

* Changes to open bdc notebooks as untitled docs. Updated tests to align with the changes

* changes: not to show untitled file as dirty and cleaned up tests in notebookService

* changes to address untitled name conflicts with open editors.

* comment cleanup

src/sql/azdata.proposed.d.ts

@@ -4485,6 +4485,11 @@ declare module 'azdata' {
 			 * Optional content used to give an initial notebook state
 			 */
 			initialContent?: nb.INotebookContents | string;
+
+			/**
+			 * A optional boolean value indicating the dirty state after the intial content is loaded, default value is true
+			 */
+			initialDirtyState?: boolean;
 		}
 
 		/**