Add event to RuntimeEventSource for AppContext switches

Fixes #56142

src/libraries/System.Private.CoreLib/src/System/AppContext.cs

@@ -135,6 +135,23 @@ public static void SetSwitch(string switchName, bool isEnabled)
             }
         }
 
+        internal static void LogSwitchValues(RuntimeEventSource ev)
+        {
+            if (s_switches is null)
+            {
+                return;
+            }
+
+            lock (s_switches)
+            {
+                foreach (var (k, v) in s_switches)
+                {
+                    // Convert bool to int because it's cheaper to log (no boxing)
+                    ev.LogAppContextSwitch(k, v ? 0 : 1);
+                }
+            }
+        }
+
 #if !CORERT
         internal static unsafe void Setup(char** pNames, char** pValues, int count)
         {

src/libraries/System.Private.CoreLib/src/System/Diagnostics/Tracing/RuntimeEventSource.cs

@@ -50,6 +50,12 @@ public static void Initialize()
         // as you can't make a constructor partial.
         private RuntimeEventSource(int _) { }
 
+        [Event(2, Level = EventLevel.Informational)]
+        internal void LogAppContextSwitch(string switchName, int value)
+        {
+            base.WriteEvent(2, switchName, value);
+        }
+
         protected override void OnEventCommand(EventCommandEventArgs command)
         {
             if (command.Command == EventCommand.Enable)
@@ -87,6 +93,8 @@ protected override void OnEventCommand(EventCommandEventArgs command)
                 _ilBytesJittedCounter ??= new PollingCounter("il-bytes-jitted", this, () => System.Runtime.JitInfo.GetCompiledILBytes()) { DisplayName = "IL Bytes Jitted", DisplayUnits = "B" };
                 _methodsJittedCounter ??= new PollingCounter("methods-jitted-count", this, () => System.Runtime.JitInfo.GetCompiledMethodCount()) { DisplayName = "Number of Methods Jitted" };
                 _jitTimeCounter ??= new IncrementingPollingCounter("time-in-jit", this, () => System.Runtime.JitInfo.GetCompilationTime().TotalMilliseconds) { DisplayName = "Time spent in JIT", DisplayUnits = "ms", DisplayRateTimeScale = new TimeSpan(0, 0, 1) };
+
+                AppContext.LogSwitchValues(this);
             }
 
         }