Set up a place holder tile for desktop

Create a placeholder tile in recents for desktop.
It is based on launcher task information. With extra flag indicating it
is for desktop.
When it is clicked, it will call sysui to show apps on desktop.

Test: manually verify that desktop tasks do not show up separately in
recents
Bug: 244348395

Change-Id: I8535a54e1545841cd988d4770e6fc5e857277cda