Remove EmbeddedVector from utils.h

Bug: v8:8834, v8:8912
Change-Id: I04e9f12121757bd0b87c68d7a4a5b213c2d8b686
Reviewed-on: https://chromium-review.googlesource.com/c/1486473Reviewed-by: Yang Guo <yangguo@chromium.org>
Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
Commit-Queue: Sigurd Schneider <sigurds@chromium.org>
Cr-Commit-Position: refs/heads/master@{#59854}