Improves performance for Draw calls by 3-5% according to a shady
benchmark.
Improves memory layout, since the values are not on the heap anymore but
in the using class.
Reduces complexity of the implementation and increases type safety.
Allows specifying default values at setting value construction time,
refs D2242.
Inspired by Vladislav introducing members that cached GetSetting values
in c016a74309/D325, refs #4039, ee38f0db37/D763, refs 4225,
a1c4c23ce4/D474, D406, which were formerly proposed to be removed in
D2241.
Differential Revision: https://code.wildfiregames.com/D2313
Tested on: clang 8.0.1, gcc 9.1.0, Jenkins vs2015
Comments By: Vladislav
This was SVN commit r23005.
