FR: Improve Mullvad exit-node selection lists on Windows and Android

### What are you trying to do?

There's a lot of Mullvad exit nodes, and no stats to help users identify which particular exit node is the best available. (I'm not even going to get into the hell that is the current exit-node selector for Windows and Android. You know it needs work.)

### How should we solve this?

In the exit node selector, nodes are probably going to be organized in nested menus by country > city > server list. I propose that at the top of each nested list, you provide a "best available" option that automatically chooses a server by load and latency.

On the country list, it'd pick the best server globally. On the city list, it'd pick the best server in that country. On the server list for a city, it'd pick the best node in that city.

### What is the impact of not solving this?

Currently, when I need an exit node, I'm finding the country or city I want and picking at random, hoping that enough others are doing the same that I wind up on a not-overloaded server with a decent ping.

### Anything else?

No clue if this is possible, but hey, it'd be nice.