Speed up `waitForMember` if user already in room (#11110)
* Speed up `waitForMember` if user already in room
`waitForMember` waits for a user to join, or be invited, to a room. But if the
user is already in the room (ie, we miss the `NewMember` event), we end up
timing out after 1500ms.
We can save 1.5s here by returning immediately.
* fix strict type errors
* stfu SonarCloud