Wait for broadcast idle before runThenWaits containing resumeTiming.

Some of the runThenWaitForBroadcasts, runThenWaitUntilBootCompleted,
runThenWaitUntilSwitchCompleted methods contain mRunner.resumeTiming()
inside their runnables in order to exclude initialisation of those
methods from timing. But then since mRunner.resumeTiming() calls
wait-for-broadcast-idle, that sometimes cause helper waiters to fail
with timeouts. To prevent that flakiness, this CL makes sure the
broadcast queue is idle before calling those helper waiters.

Bug: 200217686
Test: atest MultiUserPerfTests:android.multiuser.UserLifecycleTests --no-bazel-mode
Change-Id: Iec97d314f661c9656c46873a641ef6b496dd260d