of VK_KHR_shader_float_controls.
The introduction of shaderSignedZeroInfNanPreserveFloat32 was causing Metal
fast math to be aggressively disabled by the use of SignedZeroInfNanPreserve
in shaders in some apps, causing a regression in shader performance in those apps.
- Change MVKConfiguration::fastMathEnabled from bool to enumeration to distinguish
between always using fast math or allowing shaders to selectively disable it.
- Default value to fast math always.