Report saga audit misconfigurations more prominently

[DavidBoike]

• Alternative to Stop forwarding SagaAudit messages from the primary instance to the audit instance #4177

ServiceControl 5 stopped ingesting saga audit messages in the primary/error instance, and instead began forwarding them to the audit instance as a workaround. The original intent was to remove this forwarding in the next major version.

However, removing that capability gains very little in terms of code to maintain or coupling, and instead would make saga audits sent to the wrong place result in a cryptic deserialization exception and a message in the ServiceControl error queue that is difficult to remedy.

Instead, this PR embraces the self-healing aspect of the forwarding strategy, while raising the log message from a warning to an error, and making it more prominent by surfacing the problem as a custom check that would be visible within ServicePulse.