Add pendingAppearedIntent to TaskFragmentContainer

1. When an activity is launched without specifying launch TaskFragment,
   it may be placed to the primary TaskFragment of a split if all
   activities in secondary split are finishing. In this case, we still
   want to check if activity should be splitted with the activity below.

   In order to do that, we need to know if it should be split with the
   secondary TaskFragment, which may still be empty, so store the
   pending appeared Intent until the TaskFragment becomes non-empty.

   i.  The secondary TaskFragment can be empty when the primary trys to
       start the secondary during #onCreated.
   ii. If the Intent never actually started, it will trigger
       #onTaskFragmentAppearEmptyTimeout to update the existing top
       container.

2. When we are finishing a TaskFragment, we used to finish all
   activities in it as well. We should not do that for activity that is
   requested to be reparented (as pending appeared).

Fix: 233684054
Test: atest WMJetpackUnitTests:TaskFragmentContainerTest
Test: atest WMJetpackUnitTests:SplitControllerTest
Change-Id: I47329b23709da7e069a6a0c84124a3d7d08aae12