Add config to sort origin branches by last commit

[ArchaicDebugger]

Pretty much a cheap and shameless implementation of @apaatsio's suggestion in 1412: https://github.com/jesseduffield/lazygit/issues/1412 there's really nothing to add there, works like a charm and is super quick.

Guessed not everyone wants the suggestion as default behavior though so I added a configuration flag - I still think the default should be set to 'ordered by last commit' since it's very useful, but I'm not sure.

Would love to start contributing more and this looked like a good way to get my hands dirty.