tpl-host-generic: Check related vars

[thesefer]

Describe the solution you'd like

We have several hosts which are a bit slow and therefore alert too early. Sometimes a short interruption which does not necessarily mean the host is down (i.e. a PDU).

It would be great if you could set the template specific variables: max_check_attempts, check_interval, retry_interval, check_timeout on a per host basis instead of changing the whole template.

Additional context

No response