Fix two more places where StringToBigInt differs from parseInt:
  - Binary and octal radix prefixes are supported
  - Trailing non-whitespace junk is not allowed

This is done with a new Behavior enum in BigIntParseIntHelper,
along with a couple of bool configuration flags in StringToIntHelper.

Bug: v8:6791, v8:7038
Change-Id: Ib91bfc5ccb04ad0dd6c99bc81e19c1239264a469
Reviewed-on: https://chromium-review.googlesource.com/764595Reviewed-by: Jakob Kummerow <jkummerow@chromium.org>
Reviewed-by: Georg Neis <neis@chromium.org>
Commit-Queue: Adam Klein <adamk@chromium.org>
Cr-Commit-Position: refs/heads/master@{#49335}