* cmd/k8s-operator,k8s-operator,go.mod: optionally create ServiceMonitor
Adds a new spec.metrics.serviceMonitor field to ProxyClass.
If that's set to true (and metrics are enabled), the operator
will create a Prometheus ServiceMonitor for each proxy to which
the ProxyClass applies.
Additionally, create a metrics Service for each proxy that has
metrics enabled.
Updates tailscale/tailscale#11292
Signed-off-by: Irbe Krumina <irbe@tailscale.com>
