Enable lint rules for Promise handling to discourage misuse of them. (#2607)

* Enable lint rules for Promise handling to discourage misuse of them.
Squashed all of Hugh's commits into one.

---------

Co-authored-by: Hugh Nimmo-Smith <hughns@element.io>

src/home/CallList.test.tsx

@@ -22,7 +22,7 @@ describe("CallList", () => {
     );
   };
 
-  it("should show room", async () => {
+  it("should show room", () => {
     const rooms = [
       {
         roomName: "Room #1",