Inherit smallest width if TF is not multi-window without bounds override

So the embedded TaskFragment in fullscreen mode can have the same
configuration as in a normal fullscreen task. Such as the fullscreen
mode parent's smallestScreenWidthDp is calculated based on all
rotations, while the multi-window mode child calculates the value
by current size.

Bug: 256787005
Test: atest TaskFragmentTest#testOnConfigurationChanged
Change-Id: Ib79c6dc443cc0688b06035ddf64fe4dd766616a0