It was a std::list for no obvious reason. This CL turns it into a
vector, which is the standard data structure we use if we don't have
any special requirements.

R=mstarzinger@chromium.org

Change-Id: Iefc321db9327e0743772dd804e2325266a9bff64
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1594727Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#61235}