RepresentationChanger::GetTaggedPointerRepresentation did not handle
kCompressed cases correctly for BigInts. This led to a crash of BigInt
benchmarks in js-perf-test.

Bug: v8:9407
Change-Id: Id1d60a81afc528c8d4180bd5de9d237f2f0abd0a
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1701848Reviewed-by: Georg Neis <neis@chromium.org>
Reviewed-by: Sigurd Schneider <sigurds@chromium.org>
Commit-Queue: Sigurd Schneider <sigurds@chromium.org>
Cr-Commit-Position: refs/heads/master@{#62718}