Encapsulate logic from Isolate::CaptureSimpleStackTrace into builder class.

This CL moves most of the logic of capturing simple stack frames from the
mentioned method into a FrameArrayBuilder class. This further encapsulates
that logic and makes it easier to refactor this code to use a callback
interface for walking the stack.

Bug: 
Change-Id: Ib0b31d9eb8c4031aa64f393982889d0d02b56639
Reviewed-on: https://chromium-review.googlesource.com/645957
Commit-Queue: Ben Titzer <titzer@chromium.org>
Reviewed-by: Jakob Gruber <jgruber@chromium.org>
Cr-Commit-Position: refs/heads/master@{#47767}