SpirvShader: Implement GLSLstd450NMax
SpirvShader: Implement GLSLstd450NMax

Beware: the dEQP tests here are very weak - they do not seem to properly test the NaN handling of this instruction.

Bug: b/126873455
Tests: dEQP-VK.spirv_assembly.instruction.compute.opnmax.all
Change-Id: Ibd704c9dc9c3475df10b02c0c0f80b9c3e472ff4
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/28710
Reviewed-by: Nicolas Capens <51edc787c30f24c4904e8ffbb5523c3a9f7a451d@google.com>
Tested-by: Ben Clayton <1f693eb7158dc33015048c09d6712f74dabddf79@google.com>
Kokoro-Presubmit: kokoro <2ac7b1f3fa578934c95181d4272be0d3bca00121@google.com>

bkaradzic/SwiftShader,bkaradzic/SwiftShader,bkaradzic/SwiftShader,google/swiftshader,google/swiftshader,bkaradzic/SwiftShader,bkaradzic/SwiftShader,google/swiftshader