Synchronize the execution of exitEmergencyMode and setEmergencyMode

In switching stacks for cross sim redialing, the execution order of
exitEmergencyMode on SIM1 and setEmergencyMode on SIM2 should be
synchronized.

To ensure the execution order, make setEmergencyMode be delayed
until exitEmergencyMode completes.

Bug: 331902867
Test: atest EmergencyStateTrackerTest
Change-Id: I847e0e1e79f9f8547f4568746aaf607e66dfbec8