Register names are static, so we do not need to access them via
RegisterConfiguration. This saves a lot of RegisterConfiguration
object creations.

R=mstarzinger@chromium.org

Bug: v8:8238
Change-Id: I295ad4d4b13fe948c70490687b7e3e9b48e70af9
Reviewed-on: https://chromium-review.googlesource.com/c/1342517Reviewed-by: Jaroslav Sevcik <jarin@chromium.org>
Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#57668}