Centralize graphics OWNERS files

Copy OWNERS files from media-libs and media-gfx to platform graphics.
The lists in the files there will be replaced by references.
Also reference the new files in the general graphics/OWNERS file.

BUG=b:208716265
TEST=None.

Change-Id: I542dbdc69bc58c74f01be966ee04865506e6a61b
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/graphics/+/3323762
Reviewed-by: David Riley <davidriley@chromium.org>
Reviewed-by: Miguel Casas-Sanchez <mcasas@chromium.org>
Commit-Queue: Ilja Friedel <ihf@chromium.org>
Tested-by: Ilja Friedel <ihf@chromium.org>
Auto-Submit: Ilja Friedel <ihf@chromium.org>
18 files changed