Use custom desktop task density on freeform launches

When a task is launched directly into freeform (meaning, the Launch
Params calculated freeform), the DesktopTasksController now also ensures
that the Desktop override density is also set in the WCT returned by
handleRequest(), otherwise the app may get inconsistent desktop
densities depending on how it entered desktop (e.g. handle drag vs
trampoline vs adb etc)

Bug: 332414819
Test: atest DesktopTasksControllerTest
Test: while already in desktop: "adb shell am start -n <pkg>/.<activity>
--windowingMode 5" - check app receives custom DW density

Change-Id: Ic204a10aef496e48a8f658e6f164db31848fe3f1