Fix for PG parameters table disappearing when trying to reset a value (#15303)

* Working on table bug

* Removed unit test checking for onEngineSettingsUpdated event to fire since removed from model

* Moved instanceofcheckbox function to utils, pr fixes

* Fix comment

extensions/arc/src/common/utils.ts

@@ -4,6 +4,7 @@
  *--------------------------------------------------------------------------------------------*/
 
 import { ResourceType } from 'arc';
+import * as azdata from 'azdata';
 import * as azurecore from 'azurecore';
 import * as vscode from 'vscode';
 import { ConnectionMode, IconPath, IconPathHelper } from '../constants';
@@ -300,6 +301,13 @@ export function convertToGibibyteString(value: string): string {
 	return String(floatValue);
 }
 
+/**
+ * Used to confirm if object is an azdata CheckBoxComponent
+ */
+export function instanceOfCheckBox(object: any): object is azdata.CheckBoxComponent {
+	return 'checked' in object;
+}
+
 /*
  * Throws an Error with given {@link message} unless {@link condition} is true.
  * This also tells the typescript compiler that the condition is 'truthy' in the remainder of the scope