Add icon when launching widgets in split

* Load the icon in the BG (though it should be
cached), then run the animation in the FG

Test: Initiating split contextually with a widget
shows icon
Bug: 293935354
Flag: ENABLE_SPLIT_FROM_WORKSPACE_TO_WORKSPACE

Change-Id: Iab1f1e9965479b0f84c74c2a5ae6e272b9a5db3a