[Metrics] Update Metrics pages w/ new Prometheus support and the renamed output rules metrics fields

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Update Metrics pages w/ new Prometheus support and the renamed output rules metrics fields.

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/assign

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See:

• [TRACKING] Expand existing webserver to serve Prometheus /metrics endpoint falco#3131
• [TRACKING] Expand Falco metrics w/ rules counters -> deprecate falco-exporter + new Grafana dashboard for Falco metrics falco#3132

Happy to edit the existing pages, but likely someone else needs to contribute a whole new page to better explain the new Prometheus integration plus Grafana dashboards.

@leogr @Issif @alacuku @sgaist