Improve RFC links (#8612)

The `tools.ietf.org` site now redirects to `www.rfc-editor.org`.
* Update various URLs to the new site.
* Make links to `www.rfc-editor.org` consistent.

Signed-off-by: SuperQ <superq@gmail.com>

man/coredns-metrics.7

@@ -1,5 +1,5 @@
 .\" Generated by Mmark Markdown Processer - mmark.miek.nl
-.TH "COREDNS-METRICS" 7 "March 2026" "CoreDNS" "CoreDNS Plugins"
+.TH "COREDNS-METRICS" 7 "October 2026" "CoreDNS" "CoreDNS Plugins"
 
 .SH "NAME"
 .PP
@@ -93,7 +93,9 @@ This plugin can only be used once per Server Block.
 .RS
 
 .nf
-prometheus [ADDRESS]
+prometheus [ADDRESS] {
+    runtime\_metrics
+}
 
 .fi
 .RE
@@ -105,6 +107,15 @@ For each zone that you want to see metrics for.
 It optionally takes a bind address to which the metrics are exported; the default
 listens on \fB\fClocalhost:9153\fR. The metrics path is fixed to \fB\fC/metrics\fR.
 
+.IP \(bu 4
+\fB\fCruntime_metrics\fR exports the full Go runtime/metrics
+\[la]https://pkg.go.dev/runtime/metrics\[ra]
+set — notably \fB\fCgo_cpu_classes_*\fR for CPU attribution (GC mark/assist/pause vs user code)
+and \fB\fCgo_sched_latencies_seconds\fR for goroutine scheduling delay. Adds roughly 100 scalars
+and 8 histograms. This is a process-wide latch: enabling it in any server block enables it
+for all, and it stays enabled across reloads until restart.
+
+
 .SH "EXAMPLES"
 .PP
 Use an alternative listening address: