This CL fixes a performance regression by conditionally compiling an
expensive instance check only in debug mode.

Bug: chromium:1329463
Change-Id: I2cceb7c06fa6db967923047a4dee63a93a0b72a2
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3743385
Commit-Queue: Camillo Bruni <cbruni@chromium.org>
Auto-Submit: Maya Lekova <mslekova@chromium.org>
Reviewed-by: Camillo Bruni <cbruni@chromium.org>
Cr-Commit-Position: refs/heads/main@{#81519}