Let fullscreen leafTask inherits windowingMode from multi-window rootTask

The test explicitly started an Activity in fullscreen windowingMode,
and the activity task was positioned in an organized multi-window
root-task. In that case, in TaskLaunchParamsModifier#calculate, the
calculated windowingMode was undefined, because the TDA was also
fullscreen, so the Task ended up as multi-window mode (inherit
from the root task).

But the resolved windowingMode was still fullscreen while calculating
the task bounds in TaskLaunchParamsModifier#calculate, so the
freeform bounds is returned and the task was updated to freeform
size while layout the Task.

This makes the Activity be launched in a smaller bounds than expected,
so as the windowMetrics of the embedding rules. So, the placeholder was
started and test failed while launching an activity on the secondary
display.

Bug: 408087047
Flag: EXEMPT bugfix
Test: MultiDisplayActivityEmbeddingPlaceholderTests

Change-Id: I1e99d415cd55e8a0fd0e51f8b61ef2e8b7594b6b