[DOC] Document the steps to expand a PVC

[git-hyagi]

Is your feature request related to a problem? Please describe. Document the steps to resize the PVC for database, redis and pulpcore pods.

Describe the solution you'd like Explain why this is a manual process, provide the steps in case the PVC allows resizing and also for migrating PV, and what should be modified in Pulp CR in case of using a new PVC.

Additional context Here are some KBs that can be helpful:

• ocp monitoring operator: https://access.redhat.com/solutions/5325711
• migrate pv (in case it is not possible to expand): https://access.redhat.com/solutions/5794841
• resize vsphere vmfs pvc: https://access.redhat.com/solutions/5140131

and also a very good step by step guide from AAP team: https://issues.redhat.com/browse/AAP-13398?focusedId=22500151&page=com.atlassian.jira.plugin.system.issuetabpanels%3Acomment-tabpanel#comment-22500151