Update digital_ocean_monitoring_alerts with the latest list of possible alert types

[elcfd]

SUMMARY

Currently the digital_ocean_monitoring_alerts only has a subset of the possible monitoring alert types.

Need to add the missing alert types.

ISSUE TYPE

• Feature Idea

COMPONENT NAME

digital_ocean_monitoring_alerts

ADDITIONAL INFORMATION

Complete list of alerts can be found here

[elcfd]

Have updated the docs for digital_ocean_monitoring_alerts_info module to remove droplets from the docs as monitoring alerts can now reference droplets, load balancers and databases.