trace2: add initial functionality

Add initial TRACE2 functionality, including:

1. The ability to add writers (which will eventually write to Normal, Perf, and Event
format targets).
2. An abstract Trace2Message class.
3. Logic to send Trace2Messages to writers.
4. Ability to release writers prior to application exit.

Author: Lessley Dennington

src/shared/Core/ITrace2Writer.cs

@@ -0,0 +1,10 @@
+using System;
+
+namespace GitCredentialManager;
+
+public interface ITrace2Writer : IDisposable
+{
+    bool Failed { get; }
+
+    void Write(Trace2Message message);
+}

src/shared/Core/Trace2.cs

@@ -0,0 +1,109 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using Newtonsoft.Json;
+using Newtonsoft.Json.Converters;
+using Newtonsoft.Json.Serialization;
+
+namespace GitCredentialManager;
+
+/// <summary>
+/// The different event types tracked in the TRACE2 tracing
+/// system.
+/// </summary>
+public enum Trace2Event
+{ }
+
+/// <summary>
+/// Represents the application's TRACE2 tracing system.
+/// </summary>
+public interface ITrace2 : IDisposable
+{ }
+
+public class Trace2 : DisposableObject, ITrace2
+{
+    private readonly object _writersLock = new object();
+    private List<ITrace2Writer> _writers = new List<ITrace2Writer>();
+
+    protected override void ReleaseManagedResources()
+    {
+        lock (_writersLock)
+        {
+            try
+            {
+                for (int i = 0; i < _writers.Count; i += 1)
+                {
+                    using (var writer = _writers[i])
+                    {
+                        _writers.Remove(writer);
+                    }
+                }
+            }
+            catch
+            {
+                /* squelch */
+            }
+        }
+
+        base.ReleaseManagedResources();
+    }
+
+    private void AddWriter(ITrace2Writer writer)
+    {
+        ThrowIfDisposed();
+
+        lock (_writersLock)
+        {
+            // Try not to add the same writer more than once
+            if (_writers.Contains(writer))
+                return;
+
+            _writers.Add(writer);
+        }
+    }
+
+    private void WriteMessage(Trace2Message message)
+    {
+        ThrowIfDisposed();
+
+        lock (_writersLock)
+        {
+            if (_writers.Count == 0)
+            {
+                return;
+            }
+
+            foreach (var writer in _writers)
+            {
+                if (!writer.Failed)
+                {
+                    writer.Write(message);
+                }
+            }
+        }
+    }
+}
+
+public abstract class Trace2Message
+{
+    private const int SourceColumnMaxWidth = 23;
+    protected const string TimeFormat = "yyyy'-'MM'-'dd'T'HH':'mm':'ss'.'ffffff'Z'";
+
+    [JsonProperty("event", Order = 1)]
+    public Trace2Event Event { get; set; }
+
+    [JsonProperty("sid", Order = 2)]
+    public string Sid { get; set; }
+
+    [JsonProperty("thread", Order = 3)]
+    public string Thread { get; set; }
+
+    [JsonProperty("time", Order = 4)]
+    public DateTimeOffset Time { get; set; }
+
+    [JsonProperty("file", Order = 5)]
+    public string File { get; set; }
+
+    [JsonProperty("line", Order = 6)]
+    public int Line { get; set; }
+}