Part 1:
Revert "PPC: skip slow tests on the ppc simulator"

This reverts commit 9dfac00a.

Part 2:
Make the slow test faster.

Bug: v8:11111
Change-Id: I8f0291098d29917fa65c4b5b28bf03cbdbe7ebc6
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3714229
Commit-Queue: Marja Hölttä <marja@chromium.org>
Reviewed-by: Shu-yu Guo <syg@chromium.org>
Cr-Commit-Position: refs/heads/main@{#81301}