This simplifies the code and removes the runtime overhead of
spontaneously adding strings to the cache.

Bug: v8:12718
Change-Id: I2ed49bd82e3baf2563eeb8f463be72c0308c52c5
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3616553Reviewed-by: Dominik Inführ <dinfuehr@chromium.org>
Reviewed-by: Leszek Swirski <leszeks@chromium.org>
Reviewed-by: Jakob Kummerow <jkummerow@chromium.org>
Reviewed-by: Tobias Tebbi <tebbi@chromium.org>
Commit-Queue: Joyee Cheung <joyee@igalia.com>
Cr-Commit-Position: refs/heads/main@{#80803}