Minor maintenance on CaravanSplittingProxy

[SokyranTheDragon]

• The cancel button will be red to match the behaviour of other session dialogs
• The proper translation key is used for travel supplies tab
• GUI.Begin/EndGroup was replaced by Widgets.Begin/EndGroup to match vanilla dialog (it seems Widgets call fixes some Unity bugs on Linux/Steam Deck)
• Removed a lot of temporary variables in DoBottomButtons
• Cleaned up CaravanUIUtility.DrawCaravanInfo call by removing default values, removing new int?(), and inverting the conditional operator

[Zetrith]

Can you take a look at the conflict?

[SokyranTheDragon]

Oops, completely forgot about this. Will try to fix it in the next 1-2 days.

[SokyranTheDragon]

I think that this should be it. I've tested it and it seemed fine on my end.