anv: Completely rework shader compilation

anv: Completely rework shader compilation

Now that we have a decent interface in upstream mesa, we can get rid of all
our hacks.  As of this commit, we no longer use any fake GL state objects
and all of shader compilation is moved into anv_pipeline.c.  This should
make way for actually implementing a shader cache one of these days.

As a nice side-benifit, this commit also gains us an extra 300 passing CTS
tests because we're actually filling out the texture swizzle information
for vertex shaders.