This adds a {PrintRegister} method which prints the given register in a
readable way (e.g. "eax", ... on ia32).
This is currently only used in Liftoff. The {RegisterConfiguration}
class has the same functionality, and I plan to make
{RegisterConfiguration} also use the new {RegisterName} functions in a
follow-up CL.

R=mstarzinger@chromium.org

Bug: v8:8238, v8:8423, v8:6600
Change-Id: If03901f1d8c5b043e0097e63920ab711bd7e2d17
Reviewed-on: https://chromium-review.googlesource.com/c/1340041Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#57646}