The {ToV8Vector} method returns a {i::Vector} pointing to heap-allocated
memory, but that memory was never free'd. Since we already have a
{ToVector} method returning a {std::vector}, this CL switches to that
one instead.

R=szuend@chromium.org

Bug: chromium:1142437, v8:11107
Change-Id: I8ee0177f7dcfe2ecb435e684674b0cda6f613658
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2523198Reviewed-by: Simon Zünd <szuend@chromium.org>
Commit-Queue: Clemens Backes <clemensb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#71040}