Tweak NS type declarations in metal-cpp.h

Changes to make metal-cpp enums work nicely with RenderDoc serialization
NS::Integer -> std::int64_t
NS::UInteger -> std::uint64_t

RenderDoc serialization works with fixed sized types

renderdoc/driver/metal/official/metal-cpp.h

@@ -496,8 +496,8 @@ namespace NS
 {
 using TimeInterval = double;
 
-using Integer = std::intptr_t;
-using UInteger = std::uintptr_t;
+using Integer = std::int64_t;
+using UInteger = std::uint64_t;
 
 const Integer  IntegerMax = INTPTR_MAX;
 const Integer  IntegerMin = INTPTR_MIN;