port b7aa4c3a (r34922)

  original commit message:
  Split ToNumberStub into the entry ToNumberStub, and two new stubs,
  StringToNumberStub and NonNumberToNumberStub, which can be used when we
  already know something about the input (i.e. in various branches of the
  code stubs, or in TurboFan graphs).

  Also introduce an appropriate StringToNumber simplified operator for
  TurboFan, that is pure and is lowered to an invocation of the newly
  added StringToNumberStub.

BUG=

Review URL: https://codereview.chromium.org/1816423002

Cr-Commit-Position: refs/heads/master@{#34971}