Fix issue with relaunch of transiently-hiding task

- When a previously-pausing task is relaunched (initiated from Core)
  during a recents transition, we should only consider it to be a
  NEW_TASK state only if there are tasks that are new.  Otherwise,
  launcher will attempt to return to the app, but the recents transition
  will not consider it a return-to-app due to the NEW_TASK state
- Separately, the visibilty of the relaunched tasks needs to be updated
  in the finish transactions of the merged transition otherwise the
  visibility set by setupStartState() will clobber the merged transition
  when the original transition is finished.

  ie.
  Start Home from A (T1, setupStartState() will hide pausing task A
      (TO_BACK) in the finish transition)
  Start A (T2, since A is transiently hiding and is technically visible,
      this results in a CHANGE+MOVE_TO_TOP and setupStartState() will
      only show() task A in the start transition)
  T2 merges into T1
  T1 finishes (this applies T1's finishT followed by T2's finishT)

Bug: 386877383
Flag: EXEMPT bugfix
Test: atest WMShellUnitTests:ShellTransitionTests
Test: Open split pair of A|B, enter overview, re-launch A (or B)
      from taskbar
Change-Id: Ic9ed3371f064bfb0d0d206a8ecfcbb0d8cc4719f