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/Precise.metal

@@ -0,0 +1,14 @@
+template<typename T>
+[[clang::optnone]] T PreciseFAdd(T l, T r) {
+    return fma(T(1), l, r);
+}
+
+template<typename T>
+[[clang::optnone]] T PreciseFSub(T l, T r) {
+    return fma(T(-1), r, l);
+}
+
+template<typename T>
+[[clang::optnone]] T PreciseFMul(T l, T r) {
+    return fma(l, r, T(0));
+}