feat(status): replace domain heuristic with CNAME or direct Statuspage probe

[jared-outpost]

The current sentry status command uses a loose hostname heuristic (host.includes("status"), endsWith(".statuspage.io"), etc.) to decide whether to hit the Statuspage summary API or the self-hosted /_health/?full=1 probe.

BYK requested that we stop relying on domain-name inference and instead:

• Perform actual CNAME/DNS resolution ourselves, or
• Directly probe the target with the Statuspage summary endpoint (and fall back to /_health/?full=1 only on a clear non-Statuspage response).

This eliminates the risk of mis-classifying hosts and makes the command reliable for arbitrary self-hosted or regional Statuspage deployments.

See original discussion: #1494 (comment)