Add mainnet node canary that fails when syncing to tip fails/panics

[dconnolly]

We want to do a full sync to tip (with checkpoint sync on) that only fails and alerts/displays the failure if something bad happens when syncing to tip.

We might be able to do this at the gcloud instance group healthcheck level by grepping logs or something, but worse comes to worse we can use GH Actions to deploy a zebrad container node and just watch it run via an open ssh session and if it fails it fails the job/step, lol.