We are interested in removing the shortcut that makes it so that users
with READ on refs/* bypass the ref filter either as a whole or gate it
behind a Gerrit config.
This commit adds two rate metrics that will give an indication of how
often this is used.
Change-Id: Ia589a5edbef40a6fcb95c9a7ce6d926a9f3f2644
c84c4e609e