[VFX] Keep activation slot visible when collapsing a block

Jira: UUM-59123

When a block is collapsed the activation slot is not visible anymore.
Before:
![Unity_JyNrRODGTR](https://media.github.cds.internal.unity3d.com/user/4003/files/b9c5467d-f237-4e52-bd5c-2a9bad57bd26)

After:
![Unity_2XV2CCHlve](https://media.github.cds.internal.unity3d.com/user/4003/files/c83c5751-7340-4546-8320-1a43bfd11d5a)


Slack thread: https://unity.slack.com/archives/G1BTWN88Z/p1702479571472809

Author: julienamsellem

Packages/com.unity.visualeffectgraph/Editor/GraphView/Elements/VFXNodeUI.cs

@@ -254,7 +254,9 @@ bool SyncAnchors(ReadOnlyCollection<VFXDataAnchorController> ports, VisualElemen
 
             if (needsResync)
             {
-                var existingAnchors = container.Children().Cast<VFXDataAnchor>().ToDictionary(t => t.controller, t => t);
+                var existingAnchors = container.Children().Cast<VFXDataAnchor>()
+                    .Union(titleContainer.Query<VFXDataAnchor>().ToList())
+                    .ToDictionary(t => t.controller, t => t);
                 container.Clear();
                 for (int i = 0; i < ports.Count; ++i)
                 {
@@ -292,8 +294,6 @@ private void UpdateActivationPortPosition(VFXDataAnchor anchor)
             if (anchor.controller.isSubgraphActivation)
                 anchor.AddToClassList("subgraphblock");
 
-            var settingsCount = expanded ? m_Settings.Count : 0;
-            anchor.style.top = -26 - settingsCount * 18 - (settingsCount > 0 ? 18 : 0);
             titleContainer.AddToClassList("activationslot");
             anchor.AddToClassList("activationslot");
             AddToClassList("activationslot");
@@ -307,6 +307,16 @@ private bool UpdateActivationPortPositionIfAny()
                 var anchor = inputContainer.Children()
                     .Cast<VFXDataAnchor>()
                     .SingleOrDefault(x => x.controller == anchorController);
+
+                if (anchor != null)
+                {
+                    anchor.RemoveFromHierarchy();
+                    titleContainer.Insert(0, anchor);
+                }
+                else
+                {
+                    anchor = titleContainer.Q<VFXDataAnchor>();
+                }
                 if (anchor != null)
                 {
                     UpdateActivationPortPosition(anchor);
@@ -389,6 +399,11 @@ public IEnumerable<VFXDataAnchor> GetPorts(bool input, bool output)
                 {
                     yield return child;
                 }
+
+                if (titleContainer.Q<VFXDataAnchor>() is { } activationSlot)
+                {
+                    yield return activationSlot;
+                }
             }
             if (output)
             {

Packages/com.unity.visualeffectgraph/Editor/UIResources/uss/VFXBlock.uss

@@ -95,11 +95,6 @@ VFXEditableDataAnchor.activationslot > BoolPropertyRM > Label
     display: none;
 }
 
-VFXContextUI .VFXNodeUI.node #node-border #title.activationslot > #title-label
-{
-    margin-left: 44px;
-}
-
 #block-container .activationslot.collapsed.VFXNodeUI.node #contents > #top > #input
 {
     padding-top: 0px;

Packages/com.unity.visualeffectgraph/Editor/UIResources/uss/VFXDataAnchor.uss

@@ -101,6 +101,13 @@ VFXContextUI #output .VFXDataAnchor.port #connector
     right: -4px;
 }
 
+.activationslot.VFXDataAnchor .propertyrm {
+    margin-left: 10px;
+}
+.activationslot.VFXDataAnchor .propertyrm > #icon {
+    display: none;
+}
+
 .VFXDataAnchor.Output.hasDepth {
     border-left-width: 1px;
     margin-left: 9px;

Packages/com.unity.visualeffectgraph/Editor/UIResources/uss/VFXNode.uss

@@ -18,6 +18,7 @@
 
 .VFXNodeUI.node #node-border > #title > #title-label
 {
+    margin-left: 54px;
     flex:1 1 auto;
     overflow:hidden;
 }