Make the IsEqualTo equality type parameter a template parameter, and add
an option to skip the length check for cases where the length is known
(e.g. in string table key comparisons).

Change-Id: I893ac880ec1e830a50ba6d8f58f375ed96d6e14e
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2562247
Auto-Submit: Leszek Swirski <leszeks@chromium.org>
Commit-Queue: Igor Sheludko <ishell@chromium.org>
Reviewed-by: Igor Sheludko <ishell@chromium.org>
Cr-Commit-Position: refs/heads/master@{#71435}