Optimization: enable skipping past IDLE_PENDING without schedule

If the IDLE_AFTER_INACTIVE_TIMEOUT is zero, go past IDLE_PENDING without
having to set an alarm. This avoids the overhead of going to to the
AlarmManagerService unnecessarily if there is nothing to be scheduled.

Bug: 431873897
Test: atest DeviceIdleControllerTest
Flag: com.android.server.deviceidle.enable_non_scheduled_exit_from_idle_pending
Change-Id: I9c6193451e4634ed162cdad3e88f30c3d2cce4a9