Ability to save/load units preference

[acheronfail]

This makes two main changes one change:

1. Navigating in the REMOTE config menu is done with the thumbstick
   • this makes it the same as the parent config menu
   • I found it confusing that the menus worked differently
   • it also means we can use the config button to edit the units
2. Allows changing the units in the REMOTE config menu
   • units are updated live in the remote
   • units are saved and loaded from the eeprom

I've tested this and so far it's working great. 👍

If it's alright with you I might create more PRs to go through and edit the other config menus so they're all navigated the same way, to avoid user confusion.

[NicoAleman]

Hey man! Appreciate the PR. I would prefer to keep the menus as is, though. They are meant to mimic how the menus were on the Voyager V1 (for anyone coming from that remote). The current navigation is as-is because there are menu options where you are defining values. For example, defining tire diameter in the board settings, you use the thumbstick to hold up or down to dial the value (yes, ideally these are just grabbed from the controller, that's a different discussion). Having the button toggle the value works fine for a binary value like the Units parameter, but doesn't work for other config options.

[acheronfail]

Totally fair, I'll update this PR to use the thumbstick to change/save the units setting, so the menus can stay the same but users still have the option of choosing units. 👍

[NicoAleman]

Thank you! That would be awesome

[acheronfail]

Alright, that should be it. 👍 I just flashed my remote with it, and things seem fine.

When you're on the units screen, moving the thumbstick up/down will toggle the units between metric/imperial. When the toggle happens it saves and writes the units preference so it's there after a reboot, etc.