Per the spec change at [1], Abstract Relational Comparison between a
BigInt and a String converts the String to BigInt via StringToBigInt
before performing the comparison. Before this change, the String was
converted to a Number, and a BigInt/Number comparison was performed.

[1] https://github.com/tc39/proposal-bigint/pull/139

Bug: v8:6791
Change-Id: I40b4f4ddc78977adb0d44180eb58e0f9a8a70cb6
Reviewed-on: https://chromium-review.googlesource.com/1004117
Commit-Queue: Jakob Kummerow <jkummerow@chromium.org>
Reviewed-by: Georg Neis <neis@chromium.org>
Cr-Commit-Position: refs/heads/master@{#52609}