[1/n] Disable DesktopModeLaunchParamsModifier if not entering desktop

`DesktopModeLaunchParamsModifier` previously always ran regardless of if
we were in/entering desktop. Although this did not cause any issue with
fullscreen tasks, it causes problems with PIP and Bubble tasks as they
all share the common variable `mLastNonFullscreenBounds`. Instead
`DesktopModeLaunchParamsModifer` should only modify the launch params if
we are in or entering desktop mode. We know we are in desktop mode if
there are freeform tasks present on the display and we know we are
entering desktop mode if the current tasks launch mode is or is to be
set to freeform.

Flag: com.android.window.flags.disable_desktop_launch_params_outside_desktop_bug_fix
Test: atest WmTests:DesktopModeLaunchParamsModifierTests
Fixes: 396108436

Change-Id: Iec0f308e86af68ea85fac4ffd3803403c2fa6a1a