Make alerting package stateful and directly error-logging. Fix the rest of the unchecked errors.

[jshufro]

The alerting package previously was stateless and simply recreated state every time any alert was called.

Now it is stateful, and only checks config on init(). Logging is done through a logger instead of through stdout.

Fixes errcheck issues and uses newest rocketpool-go/v2 and node-manager-core commits which resolve upstream errcheck issues.

Enables all linters 🎉

[jclapis]

LGTM, have a few error messages to embellish but they won't block the PR; they can come later with the master merge.

[jclapis]

Added said embellishments in as comments.

[jclapis]

Cheers!