Use HDRenderPipelineAsset for decal atlas dimensions, print an error when decal atlas allocation fails.

ScriptableRenderPipeline/HDRenderPipeline/HDRP/Decal/DecalSystem.cs

         private Texture2DAtlas m_Atlas = null;
         public bool m_AllocationSuccess = true;
 
-        public static int kDecalAtlasWidth = 4096;
-        public static int kDecalAtlasHeight= 4096;
-
         public Texture2DAtlas Atlas
         {
             get
-                    m_Atlas = new Texture2DAtlas(kDecalAtlasWidth, kDecalAtlasHeight, RenderTextureFormat.ARGB32);
+                    m_Atlas = new Texture2DAtlas(HDUtils.hdrpSettings.decalSettings.atlasWidth, HDUtils.hdrpSettings.decalSettings.atlasHeight, RenderTextureFormat.ARGB32);
                 }
                 return m_Atlas;
             }
 
             if (!instance.m_AllocationSuccess) // texture failed to find space in the atlas
             {
+                instance.m_AllocationSuccess = true;
+                }
+                if(!instance.m_AllocationSuccess) // still failed to allocate, decal atlas size needs to increase
+                {
+                    Debug.LogError("Decal texture atlas out of space, decals on transparent geometry might not render correctly, atlas size can be changed in HDRenderPipelineAsset");
                 }
             }
         }

ScriptableRenderPipeline/HDRenderPipeline/HDRP/Decal/GlobalDecalSettings.cs

 	public class GlobalDecalSettings
 	{
 		public int drawDistance = 1000;
-		public int atlasSize = 8192;
+		public int atlasWidth = 4096;
+        public int atlasHeight = 4096;
 	}
 }

ScriptableRenderPipeline/HDRenderPipeline/HDRP/Editor/RenderLoopSettings/GlobalDecalSettingsUI.cs

 			EditorGUILayout.LabelField(_.GetContent("Decals"), EditorStyles.boldLabel);
 			++EditorGUI.indentLevel;
 			EditorGUILayout.PropertyField(d.drawDistance, _.GetContent("Draw Distance"));
-			EditorGUILayout.PropertyField(d.atlasSize, _.GetContent("Atlas Size"));
+			EditorGUILayout.PropertyField(d.atlasWidth, _.GetContent("Atlas Width"));
+            EditorGUILayout.PropertyField(d.atlasHeight, _.GetContent("Atlas Height"));
 			--EditorGUI.indentLevel;
 		}
 	}

ScriptableRenderPipeline/HDRenderPipeline/HDRP/Editor/RenderLoopSettings/SerializedGlobalDecalSettings.cs

 		public SerializedProperty root;
 
 		public SerializedProperty drawDistance;
-		public SerializedProperty atlasSize;
+		public SerializedProperty atlasWidth;
+        public SerializedProperty atlasHeight;
 
 		public SerializedGlobalDecalSettings(SerializedProperty root)
         {
-			atlasSize = root.Find((GlobalDecalSettings s) => s.atlasSize);			
+			atlasWidth = root.Find((GlobalDecalSettings s) => s.atlasWidth);			
+            atlasHeight = root.Find((GlobalDecalSettings s) => s.atlasHeight);			
         }
 	}
 }

ScriptableRenderPipeline/HDRenderPipeline/HDRP/Material/Decal/DBufferManager.cs

             if (frameSettings.enableDBuffer)
             {
                 cmd.SetGlobalInt(HDShaderIDs._EnableDBuffer, vsibleDecalCount > 0 ? 1 : 0);
-                cmd.SetGlobalVector(HDShaderIDs._DecalAtlasResolution, new Vector2(DecalSystem.kDecalAtlasWidth, DecalSystem.kDecalAtlasHeight));
+                cmd.SetGlobalVector(HDShaderIDs._DecalAtlasResolution, new Vector2(HDUtils.hdrpSettings.decalSettings.atlasWidth, HDUtils.hdrpSettings.decalSettings.atlasHeight));
                 BindBufferAsTextures(cmd);
             }
             else

ScriptableRenderPipeline/HDRenderPipeline/HDRP/Texture2DAtlas.cs

                 m_Height,
                 1,
                 DepthBits.None,
-                RenderTextureFormat.ARGB32,
+                m_Format,
                 FilterMode.Point,
                 TextureWrapMode.Clamp,
                 TextureDimension.Tex2D,