This reverts commit 07e11a64.

Reason for revert: caused regressions and heap verification failures

Bug: chromium:1330410, chromium:1330408, chromium:1330413

Original change's description:
> [heap] pre-populate the single_character_string_cache
>
> 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/+/3616553
> Reviewed-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}

Bug: v8:12718
Change-Id: I569fea9e34effd57c9e7c65190cf5b4ec0b0623b
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3679680
Commit-Queue: Leszek Swirski <leszeks@chromium.org>
Bot-Commit: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
Reviewed-by: Leszek Swirski <leszeks@chromium.org>
Owners-Override: Leszek Swirski <leszeks@chromium.org>
Cr-Commit-Position: refs/heads/main@{#80870}