[UUM-66201] Fixed static numDecalsThisFrame causing IndexOutOfRange exceptions

Fix [UUM-66021](https://jira.unity3d.com/browse/UUM-66021)
Fixed IndexOutOfRange errors in the decal system when using multiple cameras. This was caused by the static variable `m_DecalsVisibleThisFrame` being updated during culling, so the number of decals visible were only considered for the last camera the decal culling ran on.

Author: laylaarab

Packages/com.unity.render-pipelines.high-definition/Runtime/Material/Decal/DecalSystem.cs

@@ -42,6 +42,14 @@ static class DecalShaderIds
 
         public class CullResult : IDisposable
         {
+           int m_NumResults;
+
+            public int numResults
+            {
+                get => m_NumResults;
+                set => m_NumResults = value;
+            }
+
             public class Set : IDisposable
             {
                 int m_NumResults;
@@ -1354,7 +1362,7 @@ private int QueryCullResults(CullRequest decalCullRequest, CullResult cullResult
 
         public void EndCull(CullRequest cullRequest, CullResult cullResults)
         {
-            m_DecalsVisibleThisFrame = QueryCullResults(cullRequest, cullResults);
+            cullResults.numResults = QueryCullResults(cullRequest, cullResults);
             foreach (var pair in m_DecalSets)
                 pair.Value.EndCull(cullRequest[pair.Key]);
         }
@@ -1670,6 +1678,7 @@ public void RenderDebugOverlay(HDCamera hdCamera, CommandBuffer cmd, int mipLeve
 
         public void LoadCullResults(CullResult cullResult)
         {
+            m_DecalsVisibleThisFrame = cullResult.numResults;
             using (var enumerator = cullResult.requests.GetEnumerator())
             {
                 while (enumerator.MoveNext())