Move NativeRegisterContextLinux/RegisterContextPOSIX*_arm to RegisterInfoAndSetInterface

This patch removes register set definitions and other redundant code from
NativeRegisterContextLinux/RegisterContextPOSIX*_arm. Register sets are now
moved under RegisterInfosPOSIX_arm which now uses RegisterInfoAndSetInterface.
This is similar to what we earlier did for AArch64.

Reviewed By: labath

Differential Revision: https://reviews.llvm.org/D86962