Update the cutout side override doc to encourage all side override

The default behavior of the display cutout rotation is to stick to the
same physical display side. If one target rotation is rotated from two
different rotations whose physical sides of the display cutout are
different, the cutout side at the target rotation can be different. This
is very likely to be the undesired behavior.

Update the doc to further elaborate the details and encourage all sides
override.

Bug: 302387383
Test: Rotate from 270 to 0 on movable cutout device and see no black
      bar underneath the status bar.
Test: LocalDisplayAdapterTest
Change-Id: Ia53a04e1d2fa12bf33d5e0e595954730448b6fac