Shader: Bias textureGather instructions on AMD/Intel (#4703)

* Experimental (GLSL, forced)

* SPIR-V attempt

* Add capability

* Fix pCount == 1 on glsl

* Fix typo

Ryujinx.Graphics.Shader/IGpuAccessor.cs

@@ -196,6 +196,15 @@ namespace Ryujinx.Graphics.Shader
             return false;
         }
 
+        /// <summary>
+        /// Queries host's gather operation precision bits for biasing their coordinates. Zero means no bias.
+        /// </summary>
+        /// <returns>Bits of gather operation precision to use for coordinate bias</returns>
+        int QueryHostGatherBiasPrecision()
+        {
+            return 0;
+        }
+
         /// <summary>
         /// Queries host about whether to reduce precision to improve performance.
         /// </summary>