afterrequestdevice event is not shown if you cancel/otherwise error

[microbit-matt-hillsdon]

Python does this, presumably as a workaround:

  private async handleWebUSBError(
    e: any,
    userAction: ConnectionAction,
    finalFocusRef: FinalFocusRef
  ) {
    if (e instanceof DeviceError) {
      this.device.dispatchTypedEvent(
        "afterrequestdevice",
        new AfterRequestDevice()
      );

We should switch to try/finally in the connection library and remove this workaround on debug.

Check for the same bug in the bluetooth code.