Steal focus in Connect after successfully installing VNet daemon

[ravicious]

On macOS, clicking on "Connect" next to a TCP app should start VNet and copy the public address of the app to clipboard. That is not the case when the user clicks on the button for the first time.

When VNet is run for the first time, we have to install a background item for the VNet daemon. The user needs to interact with a system notification and then a system auth dialog. During all of this, the Electron app loses focus. So when the button event handler sees that the VNet daemon got installed and tries to copy the app address to the clipboard, it cannot do so because of Chromium's policy for clipboard manipulation which doesn't let the browser APIs modify the clipboard if Chromium window is not focused.

To work around this, we should make sure that the renderer window is focused once the app knows that the daemon got installed.

• Steal focus after successfully installing VNet daemon.
• Adjust the notification message for single-port apps so that it says "Connect via VNet by using <address> and any port.
• Investigate if the same issue exists on Windows.