Revert "Reland "[VM runtime] Switch intrinsics from old to new Bigint implementation.""
Revert "Reland "[VM runtime] Switch intrinsics from old to new Bigint implementation.""

This reverts commit be62fff82f6c8991af58a8356d1572727e2b0a27.

Reason for revert: See https://github.com/dart-lang/sdk/issues/32465

Original change's description:
> Reland "[VM runtime] Switch intrinsics from old to new Bigint implementation."
> 
> The change was reverted (thanks Slava) because gen_snapshot was failing to
> find the core lib class _BigIntImpl on flutter.
> The PR https://github.com/flutter/engine/pull/4735 fixed that issue on flutter.
> 
> Change-Id: Id6863d79f7fdb17f0076b63b0168394d5e95ec8d
> Reviewed-on: https://dart-review.googlesource.com/44660
> Reviewed-by: Alexander Markov <alexmarkov@google.com>

TBR=alexmarkov@google.com,regis@google.com

# Not skipping CQ checks because original CL landed > 1 day ago.

Change-Id: I412f5143442ca6ad43784b037c01fcf9bb42c348
Reviewed-on: https://dart-review.googlesource.com/45800
Reviewed-by: Zach Anderson <9f8b31e960a68dade71618f1ff6da6e23a1edfc9@google.com>
Reviewed-by: Siva Annamalai <2e618a8cbd7bb6b3d4409061ae407d692a098546@google.com>
Commit-Queue: Zach Anderson <9f8b31e960a68dade71618f1ff6da6e23a1edfc9@google.com>

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