Added support for edge treatment parameters for BlurShader

Added configurable parameters for edge treatment for
BlurShader to determine how edge pixels are to be
computed as part of the blur kernel. This provides
the option to sample the edge pixels of the source
for larger windows as well as using transparent
(default behavior)

Fixes: 167714368
Test: Added CTS tests to verify results of edge treatment parameters
Change-Id: I3880ff4aa2e2a4eba831a0aa6d2ec77b07e84813