docs: move and expand uninstall content

[PaulRMellor]

Signed-off-by: prmellor pmellor@redhat.com

Documentation

New Uninstalling Strimzi section in the Deploying guide

• Moves the current uninstall procedure out of the Managing section of the Configuring guide
• Creates a new assembly for uninstalling content in the Deploying guide
• Introduces a new procedure to outline the steps when uninstalling after deploying from OperatorHub.io

Checklist

Please go through this checklist and make sure all applicable tasks have been done

• Write tests
• Make sure all tests pass
• Update documentation
• Check RBAC rights for Kubernetes / OpenShift roles
• Try your changes from Pod inside your Kubernetes and OpenShift cluster, not just locally
• Reference relevant issue(s) and close them after merging
• Update CHANGELOG.md
• Supply screenshots for visual changes, such as Grafana dashboards

[strimzi-ci]

Can one of the admins verify this patch?

[michalxo]

LGTM.