Revert "GL_ext_vulkan_glsl_relaxed extension support, and cross stage aware IO mapper"

Test/vk.relaxed.errorcheck.frag

@@ -1,16 +0,0 @@
-#version 460
-
-layout (location = 0) in vec4 io;
-
-out vec4 o;
-
-// default uniforms will be gathered into a uniform block
-uniform vec4 a;     // declared in both stages with different types
-
-vec4 foo() {
-    return a;
-}
-
-void main() {
-    o = io + foo();
-}