Support the webidl bigint type in the bindings

This CL adds a helper class in core/v8 called BigInt to read the value
out of a v8::BigInt. Currently, this class only exports the value to
absl::uint128 or back to v8::BigInt, but we can add additional formats
as needed.

Fixed: 1402467
Change-Id: I57f26ba500f18f4969f937bbb3e352b983816333
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4361938
Reviewed-by: Andrey Kosyakov <caseq@chromium.org>
Reviewed-by: Caleb Raitto <caraitto@chromium.org>
Reviewed-by: Yuki Shiino <yukishiino@chromium.org>
Reviewed-by: Kentaro Hara <haraken@chromium.org>
Commit-Queue: Nate Chapin <japhet@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1123800}
NOKEYCHECK=True
GitOrigin-RevId: 968c90947aedd67382503e819e7f2dcc98fe57de
2 files changed