Add OWNERS for top-level crostestutils

Most of the subdirectories' OWNERS files set noparent.
Regardless, the existing top-level OWNERS are not useful:
* aashutoshk and achuith were added only because of their alphabetically
early names
* akeshet no longer works at Google
Hence, we need a more useful OWNERS file.

TEST=None
BUG=None

Exempt-From-Owner-Approval: The existing owners have told me that they
are not sufficiently knowledgeable about this repo.
Change-Id: I643f4dae9e52b6c4b68c29bc8168f2cdb90ccccd
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/crostestutils/+/2005109
Tested-by: Greg Edelston <gredelston@google.com>
Commit-Queue: Greg Edelston <gredelston@google.com>
Reviewed-by: Achuith Bhandarkar <achuith@chromium.org>
Reviewed-by: Sean Abraham <seanabraham@chromium.org>
diff --git a/OWNERS b/OWNERS
index 08c8f75..3ce9880 100644
--- a/OWNERS
+++ b/OWNERS
@@ -1,3 +1,4 @@
-aashutoshk@google.com
-achuith@chromium.org
-akeshet@chromium.org
+kmshelton@chromium.org
+kathrelkeld@chromium.org
+seanabraham@chromium.org
+dhanyaganesh@chromium.org