Removing obsolete call to start home activity with shell transitions

- The second start activity was causing issues with 3p launchers which
  may not expect another new intent (ie. if it handles gestures at
  the bottom of the screen).  We can't completely remove this logic
  because for button navigation we don't want to fall through to the
  launch-next-task animation below, but we can can continue to
  finish the recents animation immediately.
- With shell transitions, leashes for opening apps are always hidden
  by default so when transitioning to a 3p launcher from
  RecentsActivity we also need to show the surface if we want to
  animate it in

Bug: 289609734
Test: Set 3p Launcher as default, in both gesture & button navigation
      - Go from 3p home -> overview, then overview -> 3p home
      - Go from app -> 3p home
      - Go from app -> overview, then overview -> 3p home
      - Quickswitch from app

Signed-off-by: Winson Chung <winsonc@google.com>
(cherry picked from https://googleplex-android-review.googlesource.com/q/commit:2b3dc6f73007f8b7d97ae2972e37c5d055659c8b)
Merged-In: I6875083931de63a8097d23d180553885ed7cfb01
Change-Id: I6875083931de63a8097d23d180553885ed7cfb01