Generate DIR_METADATA files and remove metadata from OWNERS
files for v8.

R=jkummerow@chromium.org, ochang@chromium.org, yangguo@chromium.org

Bug: chromium:1113033
Change-Id: I82cbb62e438d82dbbc408e87120af39fa9da0afa
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2476680Reviewed-by: Adam Klein <adamk@chromium.org>
Reviewed-by: Maya Lekova <mslekova@chromium.org>
Reviewed-by: Jakob Kummerow <jkummerow@chromium.org>
Reviewed-by: Yang Guo <yangguo@chromium.org>
Commit-Queue: Edward Lesmes <ehmaldonado@chromium.org>
Auto-Submit: Edward Lesmes <ehmaldonado@chromium.org>
Cr-Commit-Position: refs/heads/master@{#70669}