Set up ACL for Stratum 1 Squids, only cache Geo API calls

[bedroge]

Our frontend Squids are now caching everything, which doesn't really make sense. We can/should restrict this to only Geo API calls, see https://cvmfs.readthedocs.io/en/stable/cpt-replica.html#recommended-setup and https://cvmfs-contrib.github.io/cvmfs-tutorial-2021/03_stratum1_proxies/#squid-configuration.