Notebooks: Save connection information in metadata (#13060)

* save connection info in notebook metadata

* update attachTo dropdown based on saved alias

* add setting for saving connection (default=false)

* dont show saved conn if seting off + added test

* show conn dialog if save conn name setting off

* address PR comments and fix unit test

* change connectionName to connection_name

src/sql/azdata.proposed.d.ts

@@ -77,6 +77,10 @@ declare module 'azdata' {
 		export interface ICellOutputMetadata {
 			resultSet?: ResultSetSummary;
 		}
+
+		export interface INotebookMetadata {
+			connection_name?: string;
+		}
 	}
 
 	export type SqlDbType = 'BigInt' | 'Binary' | 'Bit' | 'Char' | 'DateTime' | 'Decimal'