[FEATURE] Add support to setup ulimit (max file opened) in apache exporter service

[emepege]

Description

In order to avoid failures related with "too many open files" from a running process, we have to add support to setup systemd service in case expand this threshold would be a requirement.

Why is this needed?

Because there may be some situations where expand the ulimit is required.

Additional Information

There are some roles that have already had it, for example:

https://github.com/idealista/clickhouse_role/blob/3bda7a062f6a3ae924c21c7d21b071343da57150/templates/clickhouse-server.service.j2#L14