Update icingaweb2 DB initialization code wrt. upstream changes

I’ve upgraded the Puppet module and manifests/initialize.pp seems to now do stuff we used to do ourselves with puppet-tails:files/monitoring/icingaweb2/scripts/install_icingaweb2_database. Likely we can drop some of our custom code :)

Related issues

• Related to #16173

Original created by @intrigeri on 12451 (Redmine)