simplify TeamsDropdown component and update ManageHostPage to keep po… (#7606)

* simplify TeamsDropdown component and update ManageHostPage to keep policy filter across team change

* fix TeamDropdown for users not on global team

frontend/test/test-utils.tsx

@@ -0,0 +1,23 @@
+import React from "react";
+import { render, RenderOptions } from "@testing-library/react";
+
+import { AppContext, IAppContext, initialState } from "context/app";
+
+type RenderOptionsWithProviderProps = RenderOptions & {
+  contextValue: Partial<IAppContext>;
+};
+
+/**
+ * A custom render method that provides a configurable App context when testing components
+ */
+// eslint-disable-next-line import/prefer-default-export
+export const renderWithAppContext = (
+  component: React.ReactNode,
+  { contextValue, ...renderOptions }: RenderOptionsWithProviderProps
+) => {
+  const value: IAppContext = { ...initialState, ...contextValue };
+  return render(
+    <AppContext.Provider value={value}>{component}</AppContext.Provider>,
+    renderOptions
+  );
+};