Add unit test framework for QDS Extension (#23776)

* Query store unit test infra setup

* Update yarn.lock file

* Update tests for utils.ts

* Move test utilities interfaces and functions to its own file

extensions/query-store/package.json

@@ -56,5 +56,10 @@
     "vscode-nls": "^4.0.0"
   },
   "devDependencies": {
+    "@microsoft/azdata-test": "^3.0.1",
+    "@microsoft/vscodetestcover": "^1.2.1",
+    "@types/mocha": "^7.0.2",
+    "should": "^13.2.1",
+    "typemoq": "^2.1.0"
   }
 }