Handle incompatible activity given null task in DMLPM

If no task is present during the calculation of the launch params in
DesktopModeLaunchParamsModifier, use available information about the
launching activity to determine incompatability. This prevents the
freeform windowing mode from being applied prematurely and needing
re-parenting down the line if the launching task and activity is
incompatible.

Flag: com.android.window.flags.handle_incompatible_tasks_in_desktop_launch_params
Fixes: 424100970
Test: atest WmTests:DesktopModeLaunchParamsModifierTests
Change-Id: I29efa9007a64209561039c3c7b99d7b6bfea4e7b