Servicemonitor metric relabeling

[bartlett-ops]

Why do we need this PR?

This PR allows custom metric relabeling rules to be applied to the web-servicemonitor resource. This allows the user to consolidate duplicate metrics generated when running the web service in HA. I've left an example on how to do this in the values.yaml comments

Changes proposed in this pull request

• Add variable web.prometheus.ServiceMonitor.metricRelabelings

Contributor Checklist

Are the following items included as part of this PR? Please delete checkbox items that don't apply.

• [x] Variables are documented in the README.md

Reviewer Checklist

• [ ] Code reviewed
• [ ] Topgun tests run
• [ ] Back-port if needed

[xtremerui]

Hi LGTM. Could you also bump the chart version?

[bartlett-ops]

Done