Add DEBUG flag for rounded corner and display cutout path

There wasn't a good approach for engineers to distignlish bounds between
H/W display component and S/W anti-aliasing.

Allow enable color to review the anti-aliasing effect.

Test: adb root; adb shell setprop debug.screenshot_rounded_corners true;
Test: adb shell pidof com.android.systemui |xargs -i adb shell kill -9 {}
Test: check visual following above steps
Test: atest SystemUITests
Test: atest ScreenDecorationsTest
Change-Id: I87f04b50945e1500babdf9fa7ba9cdb37010fde8
Merged-In: I87f04b50945e1500babdf9fa7ba9cdb37010fde8