Added RenderEffect property on RenderNode

Introduced RenderEffect API to handle consuming
SkImageFilter parameters on RenderNode objects
in order to support blur.

Updated SilkFX demo to use RenderEffect
APIs on RenderNode instead of BlurShader

Bug: 168549524
Test: Added tests to RenderNode CTS test cases
Change-Id: I5005a322a6d75438dd104e6915630264406cf771