Made Common namespaces more consistent

This is a follow-up on the decision we've come to in #7036.

A lot of the traits in Common still used old RA-style namespaces. This moves them to Common.Traits.

Additionally, this moves a couple more traits from RA to Common.
Can we add ```using RallyPointTrait = OpenRA.Mods.Common.RallyPoint;```
to the top and change this to ```readonly RallyPointTrait rp;```