StringBuilder and its base class SimpleStringBuilder aren't very safe
and are a potential source of memory leaks or double-frees.

This removes the StringBuilder class and converts all of its usages to
use the standard library.

(As a drive-by, this converts std::ostream* to std::ostream& which is
more idiomatic C++).

Bug: v8:11917
Change-Id: I0eaf9d60cf49836e65bb28f0e114b33ef8103a61
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2978252
Auto-Submit: Dan Elphick <delphick@chromium.org>
Commit-Queue: Santiago Aboy Solanes <solanes@chromium.org>
Reviewed-by: Santiago Aboy Solanes <solanes@chromium.org>
Reviewed-by: Clemens Backes <clemensb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#75298}