[Mesa-dev] V2 Shared shader info

[Timothy Arceri]

Having the shader info struct in nir_shader makes things difficult for
the shader cache, and means we are copying values in the glsl->nir pass
unnecessarily. This series creates a shared shader info and makes a bunch
of clean-ups based on this change.

The st changes have been tested against llvmpipe.

There is still more work to be done to remove some of the now duplicate
fields in gl_program but I'll send that in a follow up series.