Add activity interface to Recents Go view

Add an interface for recents to activity logic that can be set on the Go
recents view. This CL includes a method for the logic that should occur
when leaving recents due to having no tasks remaining.

As the view has no knowledge of the containing activity (could be
Launcher or could be a separate activity), this interface must be set
externally.

Bug: 114136250
Test: Remove all tasks, see that it goes to home when l3goIconRecents is
the default launcher
Change-Id: I110abab49c22e245b98a1f9b91b0b0f052886098