DisplayCutout: Dispatch all non-zero safeInsets

Ensures that even if the display cutout does not overlap
a window, the safe insets are still dispatched if the window
overlaps any part of the cutout area and the safe insets
are therefore non-zero.

To do that, we need to compute the insets once against the
display size, then only shrink or expand the safe insets
accordingly.

Bug: 73533636
Test: atest DisplayCutoutTest
Change-Id: I1ea449178e29c7effdd92cac78af1a3875ca7e70