Create the Concept of Multiple EventPipe Sessions (#24417)

This is the initial work to enable https://github.com/dotnet/coreclr/issues/15377

## What's here?

- A lot of code move/split. Some important moves:
  - `EventPipe` has a colection of `EventPipeSessions` instead of a single session.
  - `EventPipeSession` now owns a `EventPipeBufferManager` and a `EventPipeFile`
  - `EventPipeThread` now owns a collection of { EventPipeBufferManager, EventPipeBuffer }, and a collection of { EventPipeBufferManager, EventPipeBufferList }
  - There is a cap on the max number of `EventPipeSession` (64 sessions)
  - `EventPipeProvider` and `EventPipeEvent` use a 64-bit mask to keep track of the sessions that are listening to provider/events.

## What's pending?

https://github.com/dotnet/coreclr/issues/24753

src/System.Private.CoreLib/src/System/Diagnostics/Eventing/EventPipe.cs

@@ -118,12 +118,6 @@ internal EventPipeProviderConfiguration[] Providers
             get { return m_providers.ToArray(); }
         }
 
-        internal long ProfilerSamplingRateInNanoseconds
-        {
-            // 100 nanoseconds == 1 tick.
-            get { return m_minTimeBetweenSamples.Ticks * 100; }
-        }
-
         internal void EnableProvider(string providerName, ulong keywords, uint loggingLevel)
         {
             EnableProviderWithFilter(providerName, keywords, loggingLevel, null);
@@ -183,7 +177,6 @@ internal static void Enable(EventPipeConfiguration configuration)
             s_sessionID = EventPipeInternal.Enable(
                 configuration.OutputFile,
                 configuration.CircularBufferSizeInMB,
-                (ulong)configuration.ProfilerSamplingRateInNanoseconds,
                 providers,
                 (uint)providers.Length);
         }
@@ -203,7 +196,6 @@ internal static class EventPipeInternal
         internal static extern UInt64 Enable(
             string? outputFile,
             uint circularBufferSizeInMB,
-            ulong profilerSamplingRateInNanoseconds,
             EventPipeProviderConfiguration[] providers,
             uint numProviders);
 
@@ -242,7 +234,7 @@ internal static class EventPipeInternal
         internal static extern unsafe bool GetSessionInfo(UInt64 sessionID, EventPipeSessionInfo* pSessionInfo);
 
         [DllImport(JitHelpers.QCall, CharSet = CharSet.Unicode)]
-        internal static extern unsafe bool GetNextEvent(EventPipeEventInstanceData* pInstance);
+        internal static extern unsafe bool GetNextEvent(UInt64 sessionID, EventPipeEventInstanceData* pInstance);
     }
 }
 

src/System.Private.CoreLib/src/System/Diagnostics/Eventing/EventPipeEventDispatcher.cs

@@ -110,7 +110,7 @@ private void CommitDispatchConfiguration()
                 new EventPipeProviderConfiguration(NativeRuntimeEventSource.EventSourceName, (ulong) aggregatedKeywords, (uint) highestLevel, null)
             };
 
-            m_sessionID = EventPipeInternal.Enable(null, 1024, 1, providerConfiguration, 1);
+            m_sessionID = EventPipeInternal.Enable(null, 1024, providerConfiguration, 1);
             Debug.Assert(m_sessionID != 0);
 
             // Get the session information that is required to properly dispatch events.
@@ -162,7 +162,7 @@ private unsafe void DispatchEventsToEventListeners()
             while (!m_stopDispatchTask)
             {
                 // Get the next event.
-                while (!m_stopDispatchTask && EventPipeInternal.GetNextEvent(&instanceData))
+                while (!m_stopDispatchTask && EventPipeInternal.GetNextEvent(m_sessionID, &instanceData))
                 {
                     // Filter based on provider.
                     if (instanceData.ProviderID == m_RuntimeProviderID)

src/vm/diagnosticserver.h

@@ -7,10 +7,8 @@
 
 #ifdef FEATURE_PERFTRACING // This macro should change to something more generic than performance.
 
-#include <stdint.h>
 #include "diagnosticsipc.h"
 
-//! TODO: Temp class.
 enum class DiagnosticMessageType : uint32_t
 {
     ///////////////////////////////////////////////////////////////////////////
@@ -28,7 +26,6 @@ enum class DiagnosticMessageType : uint32_t
     AttachProfiler = 2048,
 };
 
-//! TODO: Temp class.
 struct MessageHeader
 {
     DiagnosticMessageType RequestType;