Move more files away from OpenRA.Mods.RA

Basically what's in this PR:
 - Moved several traits from Mods.RA to Mods.Common
 - Moved several render traits from Mods.RA to Mods.TS
 - Made TD and TS namespaces consistent with what was decided in #7036
 - Moved the Drag activity from Mods.RA to Mods.Common

**Note** : It's getting harder and harder to stay away from the `Building` trait with every following migration PR. That thing is tied up to pretty much everything - PathFinding, Movement, Attacks, Weapons, Turrets, Renders...
Either someone has to deal with  #7035 soon, or I will have to make a very big bulk migration of **a lot** of files in the near future.