allocation-builder.h was using methods defined in map-inl.h, which is
not allowed. Thus move the respective methods to
allocation-builder-inl.h.

R=mstarzinger@chromium.org

Bug: v8:7965
Change-Id: Idd040f624d7e9491bc3d4bbd1e6ab3e8cf051917
Reviewed-on: https://chromium-review.googlesource.com/c/1303297
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
Cr-Commit-Position: refs/heads/master@{#57069}