Showing starting window after activity flags applied

Starting window was shown while brought an existing task to front and
that had increased Phone hot launch time.

Before bde91e94, a single-task activity (like Phone) had the new intent set
in earlier flow and the snapshot starting window was not allowed to show if
an intent (other than main) had set, see AR#allowTaskSnapshot(). So, there
was no starting window during hot launch.

Showing starting window after activity flags are applied, where the
new intent (if any) were set, and doing so if the task had moved to front.

Bug: 141271584
Test: adb shell am instrument -w \
      -e class com.android.tests.applaunch.AppLaunch \
      -e launch_directory '/storage/emulated/0/Download' \
      -e apps 'Phone^Phone' -e trial_launch true -e force_stop_app false \
      -e launch_iterations 100 \
      com.android.tests.applaunch/android.test.InstrumentationTestRunner

Change-Id: Ic87c064840fead057ccc305e5580db1dfa806b33