Create an Alert for APNS outage

[data-sync-user]

We recently had a complete APNs outage. This was reflected in out metrics in a few ways,

One: autoendpoint.notification.bridge.error.sum {platform: apns, reason: connection_unavailable}
(see https://earthangel-b40313e5.influxcloud.net/d/do4mmwcVz/autopush-gcp?orgId=1&viewPanel=57&from=1714756175489&to=1715044974289)

Two:
autoendpoint.notification.bridge.error.sum {platform: apns} showing high activity
autoendpoint.notification.bridge.sent.sum {platform: apns} showing low activity

https://earthangel-b40313e5.influxcloud.net/d/do4mmwcVz/autopush-gcp?orgId=1&from=1714756175489&to=1715044974289&viewPanel=20

We should establish alerts around these metrics (as well as a similar set for FCM metrics) to notice outages sooner.

┆Issue is synchronized with this Jira Bug