Device Discovery Improvements: Phase 2

[TwitchBronBron]

Support adding a hand-curated list of devices that will always be in the list. (more details to come, just tracking the structure for now);

"brightscript.devices": [
	{
		"name": "guid",
		"host": "1.2.3.4",
		"password": "aaa",
		"favorite": true,
		"deviceId": "314sdfsd3"
	}
],

Other features:

• when loading "brightscript.devices", should read from ALL the different places that vscode can define them, and establish a priority order (user wins probably?). (see debugConfigurationProvider for the workspaceConfiguration.inspect example)
• better handling of when "last used device" goes away. (do we show it in the list but disabled?)
• show devices all the time in the devics panel (with some type of offline status if missing).
• figure out caching around devics only by their IP address (but you switched networks), or by deviceId (scan for devices, update ip address because deviceId wins, just for this session? Suggest updating settings?)
• add a "enable/disable broadcasting" toggle in the device panel
• if you manually type an IP address, we will "remember" that device by putting it in the devices list (and saving it in the list of devices we've seen, but treating it slightly more like all the other ones we've discovered by SSDP, not permanent).
• "hide this device". gotta think about how this works...
• Add some settings to manage various behaviors
  • "automaticDeviceScanning": "extension will scan for devices at smart times",
  • "lazyHealthChecking": "only health check devices when you interact with it (sideload to it, expand it)",
  • "whatConfigFilesToRead": [],
• probably more...

host picking behaviors (#689)