Use %_ToLength for TO_LENGTH, implemented via a ToLengthStub
that supports a fast path for small integers. Everything else is still
handled in the runtime.
CQ_INCLUDE_TRYBOTS=tryserver.v8:v8_linux_nosnap_rel
BUG=v8:4494
LOG=n
Review URL: https://codereview.chromium.org/1412963002
Cr-Commit-Position: refs/heads/master@{#31358}
