Update Logs + Infrastructure docs to specify shipper compatibility and index customization

If you look at the forums, as well as support cases, shipper compatibility with the new Infrastructure and Logs UI is one of the most frequent questions around getting started.
https://discuss.elastic.co/c/infrastructure
https://discuss.elastic.co/c/logs

Looking at our documentation, we are missing sufficient detail:
https://www.elastic.co/guide/en/infrastructure/guide/current/install-infrastructure-monitoring.html

At a minimum, I think we should add information around:
1. The fact that shippers of versions 6.5 and above are require
2. That users can customize in kibana.yml which index(es) this Logs and Infrastructure UIs looks at.

cc @alvarolobato @makwarth

Inizia dalla pagina install-infrastructure-monitoring.html collegata nell’issue e rivedi le istruzioni esistenti per la configurazione dello shipper. Verifica la compatibilità dichiarata dello shipper con 6.5+ e i dettagli della personalizzazione dell’indice in kibana.yml. Il lavoro è completato quando la documentazione di Logs e Infrastructure spiega chiaramente entrambi i requisiti.

Scritto dal modello di indicizzazione a partire dal testo della issue.