Return bounds when it's in fullscreen display.

These bounds won't be applied to the task when the windowing mode isn't
freeform. Rather, they will be applied to the last non-fullscreen bounds
which would be used to restore it back to the old bounds when display
changes to freeform.

Also fixed the unit test for this particular case.

Bug: 135941344
Bug: 135780225
Test: Manual tests on devices where display windowing mode may change at
runtime.
Test: atest WmTests:TaskLaunchParamsModifierTests

Change-Id: I137c9ab754fae6d50f61e55a19f931d03477d9b2