We have a global test/OWNERS that has "file://COMMON_OWNERS".
This CL removes redundant OWNERS files in test/ subdirectories and
removes redundant entries from OWNERS files we need to keep for
special per-file entries.

R=yangguo@chromium.org, machenbach@chromium.org
CC=​​jkummerow@chromium.org

Bug: v8:9247
Change-Id: Ic2e8cbe8e379d7d23c86c6164305e65807f28ed3
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1674024Reviewed-by: Michael Achenbach <machenbach@chromium.org>
Reviewed-by: Jakob Kummerow <jkummerow@chromium.org>
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#62336}