Rounded corner not align to right on land

1. On landscape mode, the right rounded corner shall be aligned to the
   right side, not left side
2. Add correct null check in onDisplayChanged() inside ScreenDecorations
3. ScreenDecorHwcLayer::updateRoundedCornerExistenceAndSize() shall
   compare top size

Bug: 230592960
Test: atest ScreenDecorHwcLayerTest ScreenDecorationsTest
Test: Rotate app to landscape mode and check rounded corner drawn on
      correct pos
Change-Id: Ifb62e0a74f8e3c93c2ea897fa67c4a9393096f7e