Hang in ConnectNamedPipe when using requestSingleInstanceLock

[nornagon]

We are seeing a hang in ConnectNamedPipe on some machines with Electron 18 when a second instance launches:

Thread 0
 0  ntdll.dll!NtFsControlFile + 0x14
 1  KERNELBASE.dll!ConnectNamedPipe + 0x76
 2  slack.exe!static void `anonymous namespace'::SendBackAck() [process_singleton_win.cc : 204 + 0xf]
 3  slack.exe!base::OneShotTimer::FireNow() [timer.cc : 306 + 0x2c]
 4  slack.exe!void base::internal::DelayTimerBase::OnScheduledTaskInvoked(class std::__1::unique_ptr<base::internal::TaskDestructionDetector,std::__1::default_delete<base::internal::TaskDestructionDetector> >) [timer.cc : 283 + 0x10]
[...]

I believe this is due to #31460, which added the SendBackAck function. cc @rzhao271