Rename regs (remove .r and .n suffix for reg types). [Not for merging]

Regs can now be accessed directly by name or by array index when specifying the reg type.
This removes a lot of the 'fluff'.

Any discussion on renaming of regs is welcome.

Only GPR and CP0 use named entries. The names are quite different and relate to actual reg functions, so hard to be confused. Even so, perhaps the names should be changed in some instances.
It would likely be better as an enum.
Yes that was my original idea. Although as a quick proof-of-concept I just dropped the reg type from the named as it was easier (I didn't need to change the existing union).

For a final solution, a named index would be nicer IMO. Someone on IRC brought up that it's easier to debug the regs when they are in the named union. Not sure if that's an issue.