Use RoundedCornerResDelegate to read rounded res

Most rounded corners resources were handled inside ScreenDecorations
before. Delegate rounded corner resources reading into
RoundedCornerResDelegate class.

Bug: 218951516

Test: atest ScreenDecorationsTest RoundedCornerResDelegateTest
Test: adb shell dumpsys activity service com.android.systemui
      (Check ScreenDecorations part)
Test: Manually testing rounded corner when display size, rotation
      changed on normal devices, foldable devices, and hardware-overlay
      devices
Change-Id: Ic32a995481404aca7a745b95187bcf1bc2f3ebae