Remove DisplaySettings::globalTransform

The globalTransform can be described entirely in terms of the clip
rectangle, physical display projection, and orientation, so the extra
field isn't needed. We only need it when handling rounded corners so
compute the transform there.

Bug: 137209275
Bug: 143929254
Test: slow swipe to recents to visually check rounded corners
Test: adb screencap during animations
Test: above tests in portrait and landscape orientation
Test: librenderengine_test
Change-Id: I05f63cc6ccbe7403fe158c86a8a3db5bf932e812