Fix split to pip with home-key not dismissing split properly

When pressing home-key with auto-pip activity in split screen, it will
be handled as a RECENT_DURING_SPLIT transition in DefaultMixedHandler to
mix with split transition handler and remote transition handler.
However, the auto-pip information will be appended to the transition
info and causing DefaultMixedHandler not consuming the transition due to
no registered remote transition matched, and fall-through to pip
transition handler. This updates DefaultMixedHandler to monitor such
transition in startAnimation callback to make sure nofity split
transition handler to dismiss split.

Fix: 273410079
Test: atest WMShellUtilsTests WMShellFlickerTests
Test: enable 3-buttona and compose a split pair with auto-pip activity
      press home-key to auto-pip and expand the pip window
      observed there is no split pair in overview panel.
Change-Id: I1c931c2beb7feedae571216414ed9f24b0972b3e