[Port] [2022.3] [Vulkan][URP] Fix linear fog rendering artifacts on A…

…dreno GPUs with Vulkan

Jira: https://jira.unity3d.com/browse/UUM-61728
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Packages/com.unity.render-pipelines.universal/ShaderLibrary/ShaderVariablesFunctions.hlsl

@@ -393,7 +393,8 @@ half3 MixFogColor(half3 fragColor, half3 fogColor, half fogFactor)
 {
     #if defined(FOG_LINEAR) || defined(FOG_EXP) || defined(FOG_EXP2)
         half fogIntensity = ComputeFogIntensity(fogFactor);
-        fragColor = lerp(fogColor, fragColor, fogIntensity);
+        // Workaround for UUM-61728: using a manual lerp to avoid rendering artifacts on some GPUs when Vulkan is used
+        fragColor = fragColor * fogIntensity + fogColor * (half(1.0) - fogIntensity);
     #endif
     return fragColor;
 }