Creates IDisposeOnRequestEnd and ensures UmbracoContext and UmbracoDatabase implement it, then we only dispose of these types of objects at the end of the request if they are part of the httpcontext items (U4-2738). Fixes: U4-2988 UmbracoObjectTypesExtensions is not thread safe

src/Umbraco.Core/IDisposeOnRequestEnd.cs

@@ -0,0 +1,14 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+
+namespace Umbraco.Core
+{
+    /// <summary>
+    /// Any class implementing this interface that is added to the httpcontext.items keys or values will be disposed of at the end of the request.
+    /// </summary>
+    public interface IDisposeOnRequestEnd : IDisposable
+    {
+    }
+}