feat: add debug server for tailnet coordinators (#5861)

Implements a Tailscale-like debug server for our in-memory coordinator. This should provide some visibility into why connections could be failing.
Resolves: https://github.com/coder/coder/issues/5845

![image](https://user-images.githubusercontent.com/6332295/214680832-2724d633-2d54-44d6-a7ce-5841e5824ee5.png)

coderd/rbac/object.go

@@ -150,6 +150,11 @@ var (
 	ResourceReplicas = Object{
 		Type: "replicas",
 	}
+
+	// ResourceDebugInfo controls access to the debug routes `/api/v2/debug/*`.
+	ResourceDebugInfo = Object{
+		Type: "debug_info",
+	}
 )
 
 // Object is used to create objects for authz checks when you have none in