tests: Move HLSL tests to a subdirectory.

Approved-by: Giovanni Mascellani (@giomasce)
Approved-by: Francisco Casas (@fcasas)
Approved-by: Henri Verbeet (@hverbeet)
Approved-by: Alexandre Julliard (@julliard)
Merge-Request: https://gitlab.winehq.org/wine/vkd3d/-/merge_requests/248

tests/hlsl/function-overload.shader_test

@@ -0,0 +1,40 @@
+[pixel shader fail]
+/* The same function signature cannot be defined twice. */
+
+float func(int arg)
+{
+    return 0.1;
+}
+
+float func(int arg)
+{
+    return 0.1;
+}
+
+float4 main() : sv_target
+{
+    return 0;
+}
+
+[pixel shader todo]
+/* Test a basic overload. */
+float func(int arg)
+{
+    return 0.1;
+}
+
+float func(uint arg)
+{
+    return 0.2;
+}
+
+float4 main() : sv_target
+{
+    int i = 1;
+    uint u = 1;
+    return float4(func(i), func(u), func(int2(1, 1)), func(uint2(1, 1)));
+}
+
+[test]
+todo draw quad
+probe all rgba (0.1, 0.2, 0.1, 0.2)