iris: Enable ARB_gl_spirv and ARB_spirv_extensions
This will also "unlock" OpenGL 4.6 for Iris!
When testing with piglit!1, there are only 4 failing tests more than i965. They are either also failing in Iris, or the generated test also fails with -glsl
(even for i965) indicating something might be wrong with the conversion process. Added a comment in Piglit MR.
Edited by Caio Oliveira