Clean the implementation of GL_EXT_texture_shadow_lod.

Move the parameter verifictation to a centralized place where all the builtins
are verified for correctness.

Add verification for the new builtins with version and extension check
These builtins are supported on GLSL since version 130 and GLES since
version 300.

Test/spv.ext.textureShadowLod.error.frag

@@ -0,0 +1,13 @@
+#version 450
+
+layout(binding = 0) uniform sampler2DArrayShadow s2da;
+
+layout(location = 0) out vec4 c_out;
+
+layout(location = 0) in vec4 tc;
+
+void main()
+{
+    float c = textureLod(s2da, tc, 0);
+    c_out = vec4(c);
+}