[RDA][ARM] Move functionality into RDA

Add several new helpers to RDA:
- hasLocalDefBefore
- isRegDefinedAfter
- isSafeToDefRegAt

And move two bits of logic from ARMLowOverheadLoops into RDA:
- isSafeToMove
- isSafeToRemove

Both of these have some wrappers too to make them more convienent to
use.

Differential Revision: https://reviews.llvm.org/D73460