Disable email action in code monitors if SMTP is not enabled

Created by: benvenker

currently, it's possible to set email as an action on a code monitor, even if SMTP is disabled. We should require it to be enabled if SMTP is not enabled on the instance.

cc @almeidapaulooliveira could use some design eyes here as well for look at how we might indicate/message that. My thought is we gray out email as an action option with a message to enable SMTP to send email notifications both in the create and edit screen :