Improve narration for backup and dacpac UIs (#6783)

* Added ability to specify aria-rowcount and -colcount to tables.

* Cleanup

* Adds aria role to table container so that screen-readers ignore it

src/sql/azdata.d.ts

@@ -2941,6 +2941,8 @@ declare module 'azdata' {
 		selectedRows?: number[];
 		forceFitColumns?: ColumnSizingMode;
 		title?: string;
+		ariaRowCount?: number;
+		ariaColumnCount?: number;
 	}
 
 	export interface FileBrowserTreeProperties extends ComponentProperties {