Set ServerStarted with TrySetResult since unit tests might do it twice

Author: andyleejordan

src/PowerShellEditorServices/Services/DebugAdapter/DebugEventHandlerService.cs

@@ -101,7 +101,7 @@ private void OnRunspaceChanged(object sender, RunspaceChangedEventArgs e)
                         // Sends the InitializedEvent so that the debugger will continue
                         // sending configuration requests
                         _debugStateService.WaitingForAttach = false;
-                        _debugStateService.ServerStarted.SetResult(true);
+                        _debugStateService.ServerStarted.TrySetResult(true);
                     }
                     return;
 

src/PowerShellEditorServices/Services/DebugAdapter/Handlers/LaunchAndAttachHandler.cs

@@ -210,7 +210,7 @@ public async Task<LaunchResponse> Handle(PsesLaunchRequestArguments request, Can
 
             // Sends the InitializedEvent so that the debugger will continue
             // sending configuration requests
-            _debugStateService.ServerStarted.SetResult(true);
+            _debugStateService.ServerStarted.TrySetResult(true);
 
             return new LaunchResponse();
         }
@@ -440,7 +440,7 @@ await _executionService.ExecutePSCommandAsync(
 
             if (runspaceVersion.Version.Major >= 7)
             {
-                _debugStateService.ServerStarted.SetResult(true);
+                _debugStateService.ServerStarted.TrySetResult(true);
             }
             return new AttachResponse();
         }