Describe the changes in the doc and link to your dev story

Provide info for the following steps:

1. - [x] Mandatory Add the required version to the Fix version/s field.

2. - [x] Mandatory Choose the type of documentation change.

      - [x] New topic in an existing section or new section
      - [ ] Update to an existing topic

3. - [x] Mandatory for GA content:
            
       - [x] Add steps and/or other important conceptual information here: 
       

This story is to update the hypershift addon agent to calculate the best estimates of how many HCPs the cluster can host based on studies performed by performance and scale team's sizing guidance.  https://access.redhat.com/documentation/en-us/red_hat_advanced_cluster_management_for_kubernetes/2.9/html/clusters/cluster_mce_overview#hosted-sizing-guidance.   Then generate prometheus metrics.

The new metrics are documented here https://github.com/stolostron/hypershift-addon-operator/blob/main/docs/cluster_capacity_metrics_hcp.md.

This repo-document can be added under https://github.com/stolostron/rhacm-docs/blob/2.9_stage/clusters/hosted_control_planes/hosted_sizing_guidance.adoc#sizing-calculation-example.

            
       - [x] Add Required access level for the user to complete the task here:

The user needs to have cluster-admin access to use HCP sizing metrics for planning HCPs.
       

       - [x] Add verification at the end of the task, how does the user verify success (a command to run or a result to see?)

The user can log into OCP console, go to Observe -> Metrics and query those metrics.     
     
       - [x] Add link to dev story here: https://issues.redhat.com/browse/ACM-9016

4. - [ ] Mandatory for bugs: What is the diff? Clearly define what the problem is, what the change is, and link to the current documentation: