chore: rename the internal NetworkMetrics to ToolsNetworkMetrics

The last of the three type names NGO and Netcode for Entities share. This one is internal, so no user
sees it and it is not a compile error either way: a source-declared type beats an imported one, so
NGO's own assembly would take its own and warn CS0436. But once the two namespaces converge the
warning appears in our build log for a name nobody can act on from outside, and "Unity.Netcode holds
no name that collides" is a simpler thing to be able to say than "two of the three".

ToolsNetworkMetrics keeps the suffix, so it still reads as a pair with its sibling
NullNetworkMetrics - the two INetworkMetrics implementations, one behind MULTIPLAYER_TOOLS and one
not.

Five sites in two files: the declaration, both constructors, the profiler marker and the single
construction site. Everything else that reads NetworkMetrics is a property of that name on
NetworkManager, NetworkMetricsManager or NetworkTransport, all typed INetworkMetrics and untouched.

The profiler marker keeps its old string rather than following the rename. It is what shows up in the
Profiler, and an internal rename is not a reason to move it, so nameof gives way to the literal with
a comment saying why.

Verified as far as this machine allows: runtime, editor and runtime tests all compile clean, which
covers the #else branch. The renamed class is entirely inside #if MULTIPLAYER_TOOLS and the harness
has no Unity.Multiplayer.Tools references, so that branch cannot be built here. A parse pass over the
file with the define on reports only CS0246/CS0234 for the tools types and no structural error, which
is what a class and constructor disagreeing on a name would produce. The define-on path still wants a
real editor build before this is trusted.

Author: NoelStephensUnity

com.unity.netcode.gameobjects/Runtime/Metrics/NetworkMetricsManager.cs

@@ -27,7 +27,7 @@ public void Initialize(NetworkManager networkManager)
             if (NetworkMetrics == null)
             {
 #if MULTIPLAYER_TOOLS
-                NetworkMetrics = new NetworkMetrics();
+                NetworkMetrics = new ToolsNetworkMetrics();
 #else
                 NetworkMetrics = new NullNetworkMetrics();
 #endif

…bjects/Runtime/Metrics/NetworkMetrics.cs …s/Runtime/Metrics/ToolsNetworkMetrics.cscom.unity.netcode.gameobjects/Runtime/Metrics/NetworkMetrics.cs renamed to com.unity.netcode.gameobjects/Runtime/Metrics/ToolsNetworkMetrics.cs com.unity.netcode.gameobjects/Runtime/Metrics/NetworkMetrics.cs renamed to com.unity.netcode.gameobjects/Runtime/Metrics/ToolsNetworkMetrics.cs

@@ -8,20 +8,22 @@
 
 namespace Unity.Netcode
 {
-    internal class NetworkMetrics : INetworkMetrics
+    internal class ToolsNetworkMetrics : INetworkMetrics
     {
         private const ulong k_MaxMetricsPerFrame = 1000L;
         private static readonly Dictionary<uint, string> k_SceneEventTypeNames;
         private static readonly ProfilerMarker k_FrameDispatch;
 
-        static NetworkMetrics()
+        static ToolsNetworkMetrics()
         {
             k_SceneEventTypeNames = new Dictionary<uint, string>();
             foreach (SceneEventType type in Enum.GetValues(typeof(SceneEventType)))
             {
                 k_SceneEventTypeNames[(uint)type] = type.ToString();
             }
-            k_FrameDispatch = new ProfilerMarker($"{nameof(NetworkMetrics)}.DispatchFrame");
+            // Spelled out rather than nameof: this is the name shown in the Profiler, and it
+            // should not move because the implementing type was renamed.
+            k_FrameDispatch = new ProfilerMarker("NetworkMetrics.DispatchFrame");
         }
 
         private static string GetSceneEventTypeName(uint typeCode)
@@ -85,7 +87,7 @@ private static string GetSceneEventTypeName(uint typeCode)
 
         private ulong m_NumberOfMetricsThisFrame;
 
-        public NetworkMetrics()
+        public ToolsNetworkMetrics()
         {
             Dispatcher = new MetricDispatcherBuilder()
                 .WithCounters(m_TransportBytesSent, m_TransportBytesReceived)