Add loader for recents Go.

This CL introduces a loader specific to recents Go that utilizes the
underlying recents model already built in. The class is responsible for
maintaining the data source for the recycler view and also loading the
task list and content. We also provide a hook into the recents view
class to call a load when the transition to recents starts.

Bug: 114136250
Test: Build Launcher3GoIconRecents
Change-Id: I22ce6f767852b0f37961e2fd06dfcb6475c91235