Refactor out-of-line code to represent either traps or stack checks,
and add function-entry stack checks.

R=ahaas@chromium.org

Bug: v8:6600
Change-Id: I467ccc2016f67da5562a576aeaeceba002cd04ca
Reviewed-on: https://chromium-review.googlesource.com/834208
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Reviewed-by: Andreas Haas <ahaas@chromium.org>
Cr-Commit-Position: refs/heads/master@{#50266}