Set focus app as home when launch activity with split-screen from Recents

When pre-N apps forced into split-screen mode from Recents, sysui will show
an overlay activity (ForcedResizableInfoActivity) to inform user.

Since it happens before set split-screen primary stack as
minimized stack and it will lead the split-screen top app stack as
focus stack, but actually the minimized stack should not be focusable.

Because the focused app stack is in split-screen primary stack, when user
tapping search bar in recents, due to home stask is below the top focused
app stack & it will end up no focus window found and then soft-keyboard
won't appear.

To Fix this no focus window issue, we should set home as focused stack with
moveHomeActivityToTop right after app stack launched in split-screen top &
home stack became in split-screen secondary stack.

Bug: 135282440
Test: manual as below steps:
1. Installed attached api.demos apk via adb install.
2. From all apps launch api.demos app and any other app.
3. Swipe up to goto overview screen.
4. Tap on api demos app icon > Select split screen and dock the app
   in multiwindow mode.
5. With overview apps still displaying in docked screen > Tap on quick
   search bar to type something and observe.
6. Expect the SoftKeyboard should appear.

Change-Id: I522cc0bf6424d415600a5991ea6c5477bdd6e238