Use new Fluent-based Resource Tree for all environments (#1841)

Co-authored-by: Laurent Nguyen <laurent.nguyen@microsoft.com>

src/Utils/PromiseSource.ts

@@ -0,0 +1,18 @@
+export default class PromiseSource<T = void> {
+  promise: Promise<T>;
+  resolve: (value: T) => void;
+  reject: (reason?: unknown) => void;
+
+  constructor() {
+    this.promise = new Promise((resolve, reject) => {
+      this.resolve = resolve;
+      this.reject = reject;
+    });
+  }
+
+  /** Resolves the promise, then gets off the thread and waits until the currently-registered 'then' callback run. */
+  async resolveAndWait(value: T): Promise<T> {
+    this.resolve(value);
+    return await this.promise;
+  }
+}