fix: update mono api calls to coreclr-compatible api calls (#3799)

* Migrate AppDomain.GetAssemblies() to CurrentAssemblies.GetLoadedAssemblies()

* Update CHANGELOG

---------

Co-authored-by: Emma <emma.mcmillan@unity3d.com>

Author: MiroBrodlovaUnityGit

com.unity.netcode.gameobjects/CHANGELOG.md

@@ -18,6 +18,7 @@ Additional documentation and release notes are available at [Multiplayer Documen
 
 ### Changed
 
+- First pass of CoreCLR engine API changes. (#3799)
 - Changed NetworkAnimator to use the `RpcAttribute` along with the appropriate `SendTo` parameter. (#3586)
 - Improve performance of `NetworkTransformState`. (#3770)
 

com.unity.netcode.gameobjects/Editor/NetworkManagerEditor.cs

@@ -5,6 +5,9 @@
 using Unity.Netcode.Editor.Configuration;
 using UnityEditor;
 using UnityEngine;
+#if UNITY_6000_5_OR_NEWER
+using UnityEngine.Assemblies;
+#endif
 
 namespace Unity.Netcode.Editor
 {
@@ -60,7 +63,11 @@ private void ReloadTransports()
         {
             m_TransportTypes.Clear();
 
+#if UNITY_6000_5_OR_NEWER
+            var assemblies = CurrentAssemblies.GetLoadedAssemblies();
+#else
             var assemblies = AppDomain.CurrentDomain.GetAssemblies();
+#endif
 
             foreach (var assembly in assemblies)
             {