port 5912e0f0(r34485)

  original commit message:
  Add StringLessThanStub, StringLessThanOrEqualStub, StringGreaterThanStub
  and StringGreaterThanOrEqualStub, based on the CodeStubAssembler, and
  hook them up with TurboFan (and Ignition). The stubs are currently
  essentially comparable with the StringCompareStub, which is now
  obsolete. We can later extend these stubs to cover more interesting
  cases (i.e. two byte sequential string comparisons, etc.).

BUG=

Review URL: https://codereview.chromium.org/1768013002

Cr-Commit-Position: refs/heads/master@{#34516}