Add a juju action to report on top visits by IP

During a potential DoS attack it's useful to quickly retrieve a list of most visits by IP. During a recent issue, an SRE ran the following:

juju run --application content-cache-1ss,content-cache-gs2 -- "awk '/Feb 24 11:/{print \$6}' /var/log/haproxy.log | cut -d ':' -f 1 | sort | uniq -c | sort -rn | head " | pp

This should really be a juju action so it's very obvious and easy for anyone to do this.