Revert "[objects.h splitting] Move Map and related classes."

This reverts commit 7be0159e.

Reason for revert: Breaks node integration:
https://build.chromium.org/p/client.v8.fyi/builders/V8%20-%20node.js%20integration/builds/5555

Original change's description:
> [objects.h splitting] Move Map and related classes.
> 
> BUG=v8:5402
> 
> Change-Id: I64fae0a0271eb0f1b71f4ec5d9bd5d22deb1cf59
> Reviewed-on: https://chromium-review.googlesource.com/502808
> Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
> Reviewed-by: Igor Sheludko <ishell@chromium.org>
> Reviewed-by: Jaroslav Sevcik <jarin@chromium.org>
> Commit-Queue: Marja Hölttä <marja@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#45305}

TBR=marja@chromium.org,mstarzinger@chromium.org,jarin@chromium.org,ishell@chromium.org
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=v8:5402

Change-Id: I7abbe535484f89288f11d963317e1552e1dac17f
Reviewed-on: https://chromium-review.googlesource.com/506012Reviewed-by: Michael Achenbach <machenbach@chromium.org>
Commit-Queue: Michael Achenbach <machenbach@chromium.org>
Cr-Commit-Position: refs/heads/master@{#45309}