Port b7aa4c3a

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.

R=bmeurer@chromium.org, joransiu@ca.ibm.com, mbrandy@us.ibm.com, michael_dawson@ca.ibm.com
BUG=

Review URL: https://codereview.chromium.org/1825593003

Cr-Commit-Position: refs/heads/master@{#35004}