Add sample demonstrating VK_KHR_shader_relaxed_extended_instruction

[gpx1000]

Description

Add a sample that shows how to use VK_KHR_shader_relaxed_extended_instruction and tutorial for it.

Fixes #

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[gary-sweet]

I'm not really sure what I'm expecting to see with this sample.

What I'm currently seeing is that I seem to have some seemingly random framebuffers begin displayed, and a bunch of these being printed to the console:

[info] vkQueueSubmit(): pSubmits[0] DebugPrintf:
relaxed-ext-inst demo: gid = 0
[info] vkQueueSubmit(): pSubmits[0] DebugPrintf:
relaxed-ext-inst demo: gid = 0

[Keenuts]

Hello! I looked at the SPIR-V file in this PR (relaxed_demo.comp.spv) and it seams it has no OpExtInstWithForwardRef instructions.

I don't know if GLSL emits those, but you can have a HLSL shader doing the same thing with the following code:

// RUN: %dxc %s -T cs_6_0 -spirv -fspv-target-env=vulkan1.3 -E main -fspv-debug=vulkan-with-source -O3

class A {
  void foo(uint3 gid) {
    printf("relaxed-ext-inst demo: gid = %u", gid.x);
  }
};

[numthreads(1, 1, 1)]
void main(uint3 gid : SV_DispatchThreadID)
{
  A a;
  a.foo(tid);
}

Here, one OpExtInstWithForwardRefs will be emitted as we have debug info with a class method, which brings a circular dependencies in the debug instructions.