Replace some [[maybe_unused]] annotations with commented names

Remove the [[maybe_unused]] annotation from various parameters that are
unconditionally unused and comment out their names instead. This makes
it unambiguous that the variables are unused, while making the remaining
[[maybe_unused]] annotations more reliable indicators that those
variables are in fact used in some contexts.

These parameters are mostly in overridden functions where the override
doesn't need that particular variable.

Source/Core/VideoCommon/VertexLoader_Position.cpp

@@ -24,7 +24,7 @@ constexpr float PosScale(T val, float scale)
 }
 
 template <>
-constexpr float PosScale(float val, [[maybe_unused]] float scale)
+constexpr float PosScale(float val, float /* scale */)
 {
   return val;
 }