Enhance host picker during launch

[TwitchBronBron]

Adds several improvements to the "${promptForHost}" option when launching:

• add last used separator for the last used device
• add devices/other devices for devices not last used
• add separator line to separate the enter manually option
• refresh the list any time a new device is discovered, instead of a blanket "wait 5 seconds" that was there previously
• show a loader when we think there are more devices to be discovered

Here's a preview of the feature: