trace2: remove inaccurate warning and add UI helper exit calls (#1114)

Remove warning about being unable to set up tracing from Trace2
TryParseSettings method. This method should just check to see whether
TRACE2 is enabled - if it is not, it does not need to warn the user, as
we only collect traces from those who actively choose to opt in.

Additionally, GCM's UI helpers are connected to the TRACE2 system via
the Start() call in `ApplicationBase.cs`. Since this call records
`Version` and `Start` events, ensure a corresponding `Exit` event is
called before the helper process completes.

src/shared/Atlassian.Bitbucket.UI.Avalonia/Program.cs

@@ -55,6 +55,7 @@ private static void AppMain(object o)
                     .GetAwaiter()
                     .GetResult();
 
+                context.Trace2.Stop(exitCode);
                 Environment.Exit(exitCode);
             }
         }

src/shared/Core/Trace2.cs

@@ -200,11 +200,6 @@ private void TryParseSettings(TextWriter error, IFileSystem fileSystem)
                 }
             }
         }
-
-        if (_writers.Count == 0)
-        {
-            error.WriteLine("warning: unable to set up TRACE2 tracing. No traces will be written.");
-        }
     }
 
     private void WriteVersion(
@@ -314,8 +309,9 @@ public abstract class Trace2Message
     [JsonProperty("sid", Order = 2)]
     public string Sid { get; set; }
 
+    // TODO: Remove this default value when TRACE2 regions are introduced.
     [JsonProperty("thread", Order = 3)]
-    public string Thread { get; set; }
+    public string Thread { get; set; } = "main";
 
     [JsonProperty("time", Order = 4)]
     public DateTimeOffset Time { get; set; }

src/shared/Git-Credential-Manager.UI.Avalonia/Program.cs

@@ -55,6 +55,7 @@ private static void AppMain(object o)
                     .GetAwaiter()
                     .GetResult();
 
+                context.Trace2.Stop(exitCode);
                 Environment.Exit(exitCode);
             }
         }

src/shared/Git-Credential-Manager/Program.cs

@@ -29,7 +29,7 @@ public static void Main(string[] args)
                         );
                     }
                 }
-                
+
                 //
                 // Git Credential Manager's executable used to be named "git-credential-manager-core" before
                 // dropping the "-core" suffix. In order to prevent "helper not found" errors for users who

src/shared/GitHub.UI.Avalonia/Program.cs

@@ -57,6 +57,7 @@ private static void AppMain(object o)
                     .GetAwaiter()
                     .GetResult();
 
+                context.Trace2.Stop(exitCode);
                 Environment.Exit(exitCode);
             }
         }

src/shared/GitLab.UI.Avalonia/Program.cs

@@ -54,6 +54,7 @@ private static void AppMain(object o)
                     .GetAwaiter()
                     .GetResult();
 
+                context.Trace2.Stop(exitCode);
                 Environment.Exit(exitCode);
             }
         }

src/windows/Atlassian.Bitbucket.UI.Windows/Program.cs

@@ -28,6 +28,7 @@ public static async Task Main(string[] args)
                     .GetAwaiter()
                     .GetResult();
 
+                context.Trace2.Stop(exitCode);
                 Environment.Exit(exitCode);
             }
         }

src/windows/Git-Credential-Manager.UI.Windows/Program.cs

@@ -28,6 +28,7 @@ public static async Task Main(string[] args)
                     .GetAwaiter()
                     .GetResult();
 
+                context.Trace2.Stop(exitCode);
                 Environment.Exit(exitCode);
             }
         }

src/windows/GitHub.UI.Windows/Program.cs

@@ -30,6 +30,7 @@ public static async Task Main(string[] args)
                     .GetAwaiter()
                     .GetResult();
 
+                context.Trace2.Stop(exitCode);
                 Environment.Exit(exitCode);
             }
         }

src/windows/GitLab.UI.Windows/Program.cs

@@ -28,6 +28,7 @@ public static async Task Main(string[] args)
                     .GetAwaiter()
                     .GetResult();
 
+                context.Trace2.Stop(exitCode);
                 Environment.Exit(exitCode);
             }
         }