Add cos/tools to COS source tree BUG=b/465210631 TEST=repo init & sync RELEASE_NOTE=None Change-Id: Id6176d13ab1114cd9988ce9a31fb7c3428bbd3aa Reviewed-on: https://cos-review.googlesource.com/c/cos/manifest/+/138861 Reviewed-by: Miri Amarilio <mirilio@google.com> Tested-by: Robert Kolchmeyer <rkolchmeyer@google.com> Reviewed-by: Kevin Berry <kpberry@google.com>