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

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

src/Shared/StorageUtility.ts

@@ -16,4 +16,5 @@ export enum StorageKey {
   SetPartitionKeyUndefined,
   GalleryCalloutDismissed,
   VisitedAccounts,
+  PriorityLevel,
 }