Now we can pass in the prefix size to OrderedHashTable directly from
the Derived class and have it calculate the hash table start offset
based on this.

Bug: v8:6443, v8:7569
Change-Id: I80d54b65116e18f5a0cab18eb51649adad447cce
Reviewed-on: https://chromium-review.googlesource.com/c/1333682
Commit-Queue: Sathya Gunasekaran <gsathya@chromium.org>
Reviewed-by: Toon Verwaest <verwaest@chromium.org>
Reviewed-by: Jaroslav Sevcik <jarin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#57499}