Fix PowerShellProcess.dipose() to fire the onExited event

It was only firing when the terminal was closed, not whenever the process exited
(which didn't make sense given its name and how we were using it).

Also had to be idempotent.

src/process.ts

@@ -15,7 +15,7 @@ export class PowerShellProcess {
     private static warnUserThreshold = 30;
 
     public onExited: vscode.Event<void>;
-    private onExitedEmitter = new vscode.EventEmitter<void>();
+    private onExitedEmitter?: vscode.EventEmitter<void>;
 
     private consoleTerminal?: vscode.Terminal;
     private consoleCloseSubscription?: vscode.Disposable;
@@ -31,6 +31,7 @@ export class PowerShellProcess {
         private sessionFilePath: vscode.Uri,
         private sessionSettings: Settings) {
 
+        this.onExitedEmitter = new vscode.EventEmitter<void>();
         this.onExited = this.onExitedEmitter.event;
     }
 
@@ -149,6 +150,9 @@ export class PowerShellProcess {
 
         void this.deleteSessionFile(this.sessionFilePath);
 
+        this.onExitedEmitter?.fire();
+        this.onExitedEmitter = undefined;
+
         this.consoleTerminal?.dispose();
         this.consoleTerminal = undefined;
 
@@ -230,7 +234,6 @@ export class PowerShellProcess {
         }
 
         this.logger.writeWarning(`PowerShell process terminated or Extension Terminal was closed, PID: ${this.pid}`);
-        this.onExitedEmitter.fire();
         this.dispose();
     }
 }

src/session.ts

@@ -530,13 +530,13 @@ export class SessionManager implements Middleware {
                 this.sessionSettings);
 
         languageServerProcess.onExited(
-            async () => {
+            () => {
                 LanguageClientConsumer.onLanguageClientExited();
 
                 if (this.sessionStatus === SessionStatus.Running
                     || this.sessionStatus === SessionStatus.Busy) {
                     this.setSessionStatus("Session Exited!", SessionStatus.Failed);
-                    await this.promptForRestart();
+                    void this.promptForRestart();
                 }
             });