BigInt performance benchmarks are restructured in JSTest1.json
in such a way that it is easier to run meaningful subsets of
BigInt test cases.

Bug: v8:9213
Change-Id: Ibf94bfb0f14cf8afa890927d97f920659e8b28d0
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1872390
Commit-Queue: Nico Hartmann <nicohartmann@chromium.org>
Reviewed-by: Georg Neis <neis@chromium.org>
Cr-Commit-Position: refs/heads/master@{#64468}