Since we have FindEntry, this is redudant.

This patch also
* Makes the tests for FindEntry stricter by testing the value
* Makes the OrderedNameDictionary::Add and
  SmallOrderedNameDictionary::Add consistent by using GetHash and
  using a DCHECK for the FindEntry call

Bug: v8:6443, v8:7569
Change-Id: I4859cd6735ec385c19acad6ce5cecaeac45173dd
Reviewed-on: https://chromium-review.googlesource.com/c/1382828
Commit-Queue: Sathya Gunasekaran <gsathya@chromium.org>
Reviewed-by: Toon Verwaest <verwaest@chromium.org>
Reviewed-by: Camillo Bruni <cbruni@chromium.org>
Cr-Commit-Position: refs/heads/master@{#58380}