- Rename TryBuildCompareOperationBranch to TryBuildCompareOperation
- Add CheckedInternalizedString conversion Node that checks for string
  inputs and extracts internalised Strings from ThinStrings
- Add BranchIfReferenceCompare Node
- Add runtime functions to create internalised and thin Strings
- Add deopt check to test/mjsunit/maglev/int32-branch.js

Bug: v8:7700
Change-Id: I0073c24fad9e3231c985153cd27b0b8fe6ee56f0
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3664498Reviewed-by: Leszek Swirski <leszeks@chromium.org>
Commit-Queue: Camillo Bruni <cbruni@chromium.org>
Cr-Commit-Position: refs/heads/main@{#81361}