Use the right SendEvent call in server implementations

This change fixes broken language and debug server tests by switching to a
different SendEvent implementation which ensures that the event is being
sent from the correct thread.  A true fix will be needed in the future to
ensure that all SendEvent implementations will use the correct thread for
sending event messages.

Author: daviwil

src/PowerShellEditorServices.Protocol/Server/DebugAdapter.cs

@@ -91,7 +91,7 @@ protected Task LaunchScript(RequestContext<object> requestContext)
                             // Make sure remaining output is flushed before exiting
                             await this.outputDebouncer.Flush();
 
-                            await requestContext.SendEvent(
+                            await this.SendEvent(
                                 TerminatedEvent.Type,
                                 new TerminatedEvent());
 
@@ -198,7 +198,7 @@ await this.editorSession.PowerShellContext.ExecuteScriptString(
 
             // Send the InitializedEvent so that the debugger will continue
             // sending configuration requests
-            await requestContext.SendEvent(
+            await this.SendEvent(
                 InitializedEvent.Type,
                 null);
         }

src/PowerShellEditorServices.Protocol/Server/LanguageServer.cs

@@ -232,7 +232,7 @@ private async Task HandleSetPSSARulesRequest(
             await RunScriptDiagnostics(
                     new ScriptFile[] { scripFile },
                         editorSession,
-                        requestContext.SendEvent);
+                        this.SendEvent);
             await sendresult;
         }
 
@@ -1136,7 +1136,7 @@ private Task RunScriptDiagnostics(
             EditorSession editorSession,
             EventContext eventContext)
         {
-            return RunScriptDiagnostics(filesToAnalyze, editorSession, eventContext.SendEvent);
+            return RunScriptDiagnostics(filesToAnalyze, editorSession, this.SendEvent);
         }
 
         private Task RunScriptDiagnostics(