fix(51100): ensure tsserver shuts down when parent process is killed (#51107)

* fix(51100): ensure tsserver shuts down when parent process is killed

When using IPC channel (`--useNodeIpc`) for communicating with tsserver,
the child tsserver process did not shut down on parent process disconnecting
(for example due to it being killed).

Call exit() on IPC disconnect, same as stdio-based communication did
when pipe to parent process was destroyed.

* don't duplicate inherited method

src/tsserver/nodeServer.ts

@@ -783,6 +783,10 @@ namespace ts.server {
                 process.on("message", (e: any) => {
                     this.onMessage(e);
                 });
+
+                process.on("disconnect", () => {
+                    this.exit();
+                });
             }
         }