Update prometheus guide to a working example and add Envoy metrics port

[sunjayBhatia]

Updates docs page guide instructions and sample manifests

Also removes prometheus annotations from Contour/Envoy and adds the metrics port to Envoy DaemonSet/Deployment so that Prometheus PodMonitors can reach the metrics server. The prometheus-operator project uses PodMonitors rather than annotations to configure Prometheus to discover scrape endpoints.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 81.62%. Comparing base (bd33dfc) to head (af7fbff).

❗ Current head af7fbff differs from pull request most recent head 5f3aac7. Consider uploading reports for the commit 5f3aac7 to get more accurate results

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #6269      +/-   ##
==========================================
+ Coverage   81.61%   81.62%   +0.01%     
==========================================
  Files         133      133              
  Lines       15858    15857       -1     
==========================================
+ Hits        12942    12944       +2     
+ Misses       2621     2619       -2     
+ Partials      295      294       -1     

see 11 files with indirect coverage changes

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[tsaarni]

I tested this and looks good!

Couple of comments/questions inline and also, at the top of the guide, there is still reference to the annotations that can now be removed:

contour/site/content/guides/prometheus.md

Lines 9 to 10 in 162c077

	default, annotations to gather them are in all the `deployment` yamls and they
	should work out of the box with most configurations.

[tsaarni]

I found some discussion that suggested preferring ServiceMonitor when service exists. Was there particular reason why choose PodMonitor instead of ServiceMonitor? I guess there should not be any difference at the end.

[davinci26]

We use PodMonitor internally because when the pods of Envoy become not-ready during shutdown (preStop) you end up losing prom scrapes if you use ServiceMonitor

[github-actions]

The Contour project currently lacks enough contributors to adequately respond to all PRs.

This bot triages PRs according to the following rules:

• After 14d of inactivity, lifecycle/stale is applied
• After 30d of inactivity since lifecycle/stale was applied, the PR is closed

You can:

• Ensure your PR is passing all CI checks. PRs that are fully green are more likely to be reviewed. If you are having trouble with CI checks, reach out to the #contour channel in the Kubernetes Slack workspace.
• Mark this PR as fresh by commenting or pushing a commit
• Close this PR
• Offer to help out with triage

Please send feedback to the #contour channel in the Kubernetes Slack

[sunjayBhatia]

I tested this and looks good!

Couple of comments/questions inline and also, at the top of the guide, there is still reference to the annotations that can now be removed:

contour/site/content/guides/prometheus.md

Lines 9 to 10 in 162c077

	default, annotations to gather them are in all the `deployment` yamls and they
	should work out of the box with most configurations.

I just removed that 2 sentences since the annotation part is no longer relevant

[skriss]

LGTM once linter issue is fixed

[tsaarni]

Looks good to me as well 👍