intel: Add INTEL_shader_integer_functions2 to OpenGL and Vulkan

This extension adds support for a subset of OpenCL integer functions to graphics shaders in OpenGL and Vulkan.

• Vulkan extension spec https://github.com/ianromanick/Vulkan-Docs/tree/wip/VK_INTEL_shader_integer_functions2 (merged)
• SPIR-V extension spec https://github.com/KhronosGroup/SPIRV-Registry/pull/27 (merged)
• OpenGL / GLSL extension spec: https://github.com/KhronosGroup/OpenGL-Registry/pull/331 (merged)
• glslang changes: https://github.com/KhronosGroup/glslang/pull/1990 (merged)
• Add Iris patches
• Piglit tests: piglit!46 (merged)
• Crucible tests: crucible!59 (merged)