Changing `http_listen_port` doesn't change `ServiceMonitor` podAnnotations values

[nschad]

We should update podAnnotations value if http_listen_port changes.

Original Comment:
Another concern I have -- and this is not entirely your fault because other deployments in this chart make the same mistake -- is that if http_listen_port is changed, this pod annotation will need to be changed to match.

cortex-helm-chart/values.yaml

Lines 73 to 74 in 858b6e2

	server:
	http_listen_port: 8080

It would be easier for the user if this annotation was populated by the value. You could support references in values by using tpl near toYaml. Something like {{- tpl (toYaml .) $ | nindent 8 }}.

Not a blocker, since this is already inconsistent throughout the chart.

Originally posted by @kd7lxl in #407 (comment)