Fixed default angle to be Orientation.LEFT_RIGHT

Fixed issue where in Android Q if no angle measurement
was specified the default gradient orientation of TOP_BOTTOM
was applied instead of the previous behavior of LEFT_RIGHT

Bug: 139822941
Test: Added CTS test to verify GradientDrawableTest
Change-Id: Ia8c53455740a29e1d123c90616066e16ddb4a241
(cherry picked from commit bd00e4c6)