glsl: Parse and propagate derivative_group to shader_info

glsl: Parse and propagate derivative_group to shader_info

NV_compute_shader_derivatives allow selecting between two possible
arrangements (quads and linear) when calculating derivatives and
certain subgroup operations in case of Vulkan.  So parse and propagate
those up to shader_info.h.

v2: Do not fail when ARB_compute_variable_group_size is being used,
    since we are still clarifying what is the right thing to do here.

Reviewed-by: Ian Romanick <ian.d.romanick@intel.com>