This CL adds the reduction for String#includes
and merges the reduction of String#indexOf and
String#includes in JSCallReducer.

This CL does two things:
- Add StringIndexOfIncludesVariant to distinguish
String#indexOf and String#includes.
- Add ReduceStringPrototypeIndexOfIncludes to reduce
for String#indexOf and String#includes.

Bug: v8:12732
Change-Id: Ied75485cf1511956e97ef986fc34a711aae3d1ce
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3552279Reviewed-by: Jakob Gruber <jgruber@chromium.org>
Reviewed-by: Tobias Tebbi <tebbi@chromium.org>
Commit-Queue: Tobias Tebbi <tebbi@chromium.org>
Cr-Commit-Position: refs/heads/main@{#79648}