EXPERIMENTAL: Metal backend (#441)

This is not a continuation of the Metal backend; this is simply bringing
the branch up to date and merging it as-is behind an experiment.

---------

Co-authored-by: Isaac Marovitz <isaacryu@icloud.com>
Co-authored-by: Samuliak <samuliak77@gmail.com>
Co-authored-by: SamoZ256 <96914946+SamoZ256@users.noreply.github.com>
Co-authored-by: Isaac Marovitz <42140194+IsaacMarovitz@users.noreply.github.com>
Co-authored-by: riperiperi <rhy3756547@hotmail.com>
Co-authored-by: Gabriel A <gab.dark.100@gmail.com>

src/Ryujinx.Graphics.Shader/CodeGen/Msl/HelperFunctions/FindMSBU32.metal

@@ -0,0 +1,6 @@
+template<typename T>
+inline T findMSBU32(T x)
+{
+    T v = select(x, T(-1) - x, x < T(0));
+    return select(clz(T(0)) - (clz(v) + T(1)), T(-1), v == T(0));
+}