feat: allow prometheus for only authorized users (#12121)

allow restrictions on who can access Prometheus
endpoint, additionally add prometheus as part of
diagnostics canned policy.

Signed-off-by: Harshavardhana <harsha@minio.io>

pkg/iam/policy/constants.go

@@ -76,7 +76,9 @@ var AdminDiagnostics = Policy{
 			Actions: NewActionSet(ProfilingAdminAction,
 				TraceAdminAction, ConsoleLogAdminAction,
 				ServerInfoAdminAction, TopLocksAdminAction,
-				HealthInfoAdminAction, BandwidthMonitorAction),
+				HealthInfoAdminAction, BandwidthMonitorAction,
+				PrometheusAdminAction,
+			),
 			Resources: NewResourceSet(NewResource("*", "")),
 		},
 	},