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/Explorer/Explorer.tsx

@@ -650,6 +650,8 @@ export default class Explorer {
   private _initSettings() {
     if (!ExplorerSettings.hasSettingsDefined()) {
       ExplorerSettings.createDefaultSettings();
+    } else {
+      ExplorerSettings.ensurePriorityLevel();
     }
   }