Remote restart should actually restart on Linux

[RebeccaMahany]

I rolled back remote restart in #1966 because we found in test that remote restart would just exit on Linux without restarting. This is because runNewerLauncherIfAvailable will immediately return nil if we're already running the latest version of launcher.

We probably need to add separate handling for errors.Is(err, remoterestartconsumer.ErrRemoteRestartRequested) where we re-exec the current running version of launcher.