[#60949022] Move Fail2Ban config to its own class

- Move Fail2Ban configuration to its own class to avoid polluting the
ci_environment base.pp manifest.
- Replace hardcoded IPs to be whitelisted by Fail2Ban with a hiera
array.
- Notify Fail2Ban service when jail.local file is updated.
Merge pull request #94 from alphagov/60949022-fail2ban-whitelist

[#60949022] Move Fail2Ban config to its own class