ector: code refactoring.

ector: code refactoring.

Current vector drawing requires several methods for compositing,
it's shouldnt have only masking but other blending functions
such as matte in lottie, porter&duff in android, etc.

Previously we didn't specify this method name,
just reserved the options and now we started to define the methods
with ector_renderer_composite_method() with Efl.Gfx.VG_Composite_Method
instead of mask_set().

Change-Id: I36235c23e1da6d3f138096a9425c6173eca93b88