Restored default behavior of GradientDrawable orientation

Fixed issue where GradientDrawable orientation had diverged
from the default behavior. Ensured that orientation by default
is configured to LEFT_RIGHT for xml defined GradientDrawables
and programmatically defined GradientDrawables have the
same default orientation of TOP_BOTTOM.

Refactored previous logic that would keep both the mAngle
parameter used in xml inflation and the mOrientation parameter
that is used to configure the angle of the gradient to no longer
keep these 2 values in sync.

Test: Added CTS test to verify orientation for xml and programmatically
defined GradientDrawables
Bug: 140835351
Bug: 139822941

Change-Id: I594496afe48d04d108053bf284e92bbfd3591fa3