Wmt priority execution feature (#1546)

* Execute the queries with high/low priority

* improvement made to the Cosmos client and created separate plugin class for setting priority header

* added test cases for the priority execution utility

* removed unwanted code

* fix compile time issues

* fix compile time issues

* fixed lint and stylinkg issues

* fixed lint and styling issues

* skip the lint check for src/Utils/PriorityBasedExecutionUtils.ts

* incorporating review comments, added the default priority level changes

* changed the priority to default instead of low

* removed the unwanted if condition

---------

Co-authored-by: Faiz Chachiya <faizchachiya@microsoft.com>

src/Common/Constants.ts

@@ -600,3 +600,9 @@ export const QueryCopilotSampleContainerSchema = {
     },
   },
 };
+
+export class PriorityLevel {
+  public static readonly High = "high";
+  public static readonly Low = "low";
+  public static readonly Default = "low";
+}