Add the supported metric types

[Gaganjuneja]

Description

Updates the _monitoring-your-cluster/metrics/getting-started.md to show case the type of metrics supported.

Issues Resolved
Closes #6694

Checklist

• By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license and subject to the Developers Certificate of Origin.
  For more information on following Developer Certificate of Origin and signing off your commits, please check here.

[hdhalter]

Please check the parent for this topic (parent: Trace Analytics). It's not appearing in the TOC.

[hdhalter]

If we want to keep this under Monitoring your cluster category, change the metadata at the top to:

---
layout: default
title: Metrics framework
nav_order: 1
has_children: false
has_toc: false
---

# Metrics framework
(Adds the heading 1 title. Place before the experimental paragraph.)

[Gaganjuneja]

Please check the parent for this topic (parent: Trace Analytics). It's not appearing in the TOC.

Ideally, it should not be trace analytics.

[natebower]

@Gaganjuneja @Naarcha-AWS Just a few minor changes. Thanks!