GPU: Compute Pipeline.

With the compute pipeline calculation can be offloaded to the GPU.
This patch only adds the framework for compute. So no changes for users at
this moment.

NOTE: As this is an OpenGL4.3 feature it must always have a fallback.

Use `GPU_compute_shader_support` to check if compute pipeline can be used.
Check `gpu_shader_compute*` test cases for usage.

This patch also adds support for shader storage buffer objects and device only
vertex/index buffers.

An alternative that had been discussed was adding this to the `GPUBatch`, this
was eventually not chosen as it would lead to more code when used as part of a
shading group. The idea is that we add an `eDRWCommandType` in the near
future.

Reviewed By: fclem

Differential Revision: https://developer.blender.org/D10913

source/blender/gpu/intern/gpu_shader_interface.cc

@@ -80,6 +80,8 @@ void ShaderInterface::debug_print()
   Span<ShaderInput> attrs = Span<ShaderInput>(inputs_, attr_len_);
   Span<ShaderInput> ubos = Span<ShaderInput>(inputs_ + attr_len_, ubo_len_);
   Span<ShaderInput> uniforms = Span<ShaderInput>(inputs_ + attr_len_ + ubo_len_, uniform_len_);
+  Span<ShaderInput> ssbos = Span<ShaderInput>(inputs_ + attr_len_ + ubo_len_ + uniform_len_,
+                                              ssbo_len_);
   char *name_buf = name_buffer_;
   const char format[] = "      | %.8x : %4d : %s\n";
 
@@ -117,6 +119,13 @@ void ShaderInterface::debug_print()
     }
   }
 
+  if (ssbos.size() > 0) {
+    printf("\n    Shader Storage Objects :\n");
+  }
+  for (const ShaderInput &ssbo : ssbos) {
+    printf(format, ssbo.name_hash, ssbo.binding, name_buf + ssbo.name_offset);
+  }
+
   printf("\n");
 }