[VFX][Fix] PointCache and VectorField importer priority

- Fixes https://jira.unity3d.com/browse/UUM-73877 which could lead to increase import time due to incorrect priorities between dependencies
- Add missing meta for image ref (unrelated to the fix)
- Hide deprecated Forward Decal Output from Node Search

Author: julienf-unity

Packages/com.unity.visualeffectgraph/Editor/Models/Contexts/Implementations/VFXDecalOutput.cs renamed to Packages/com.unity.visualeffectgraph/Editor/Models/Deprecated/VFXDecalOutput.cs

@@ -5,8 +5,6 @@
 
 namespace UnityEditor.VFX
 {
-    [VFXHelpURL("Context-OutputForwardDecal")]
-    [VFXInfo(name = "Output Particle|Forward Decal", category = "#6Output Deprecated")]
     class VFXDecalOutput : VFXAbstractParticleOutput
     {
         public override string name => "Output Particle".AppendLabel("Forward Decal", false);

Packages/com.unity.visualeffectgraph/Editor/Models/Contexts/Implementations/VFXDecalOutput.cs.meta renamed to Packages/com.unity.visualeffectgraph/Editor/Models/Deprecated/VFXDecalOutput.cs.meta

@@ -14,7 +14,7 @@
 
 namespace UnityEditor.VFXToolbox
 {
-    [ScriptedImporter(1, "vf")]
+    [ScriptedImporter(1, "vf", -802)]
     class VectorFieldImporter : ScriptedImporter
     {
         public enum VectorFieldOutputFormat

Packages/com.unity.visualeffectgraph/Editor/Utilities/VectorFieldImporter/Editor/VectorFieldImporter.cs

@@ -14,7 +14,7 @@
 
 namespace UnityEditor.Experimental.VFX.Utility
 {
-    [ScriptedImporter(1, "pcache")]
+    [ScriptedImporter(1, "pcache", -802)]
     class PointCacheImporter : ScriptedImporter
     {
         public static T[] SubArray<T>(T[] data, int index, int length)