--stress-opt never did what we wanted it to; it ran its runs in
different contexts (therefore not able to share feedback across runs),
and even if it didn't, each run would create new closures for any
defined closures, so we'd still more than likely end up poly- or
mega-morphic.

Fuzzers cover this use case better than --stress-opt ever did, so now
it's just using precious bot time. We can get rid of it.

Bug: v8:10386
Change-Id: Ibbb9207d887b4b1dc4ec9093858d477c0f95eb37
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3803228
Commit-Queue: Camillo Bruni <cbruni@chromium.org>
Reviewed-by: Camillo Bruni <cbruni@chromium.org>
Commit-Queue: Leszek Swirski <leszeks@chromium.org>
Auto-Submit: Leszek Swirski <leszeks@chromium.org>
Cr-Commit-Position: refs/heads/main@{#82722}