1. Proposed title of this feature request

Allow ACM to upgrade managed clusters to non-recommended versions

2. What is the nature and description of the request?

Currently, upgrading a cluster to non-recommended versions of OpenShift is only possible from the cluster and not via ACM.

oc adm upgrade --include-not-recommended
oc adm upgrade --allow-not-recommended --to <version>

The ManagedClusterInfo resource only shows recommended versions under availableUpdates. 

Example:
In the screenshots the ManagedCluster info does not fetch 4.12.45 that is a non-recommended version.
When upgrading from the cluster instead of ACM, we can see the 4.12.45 version when toggling the 'Includes supported but non-recommended versions.

Proposed Feature:

The ability to upgrade managed clusters to non-recommended versions directly via the Red Hat ACM interface and using the ClusterCurator.

This feature should include:

• Visibility of non-recommended versions in the ACM UI upgrade page (same as in the clusters upgrade page)

• Option to select and upgrade to non-recommended versions, with appropriate warnings and disclaimers.

• Use the ClusterCurator to upgrade to these non-recommended versions

3. Why does the customer need this? (List the business requirements here)

The customer has automated the of managed clusters upgrade using the ClusterCurator but is not able to upgrade to non-recommended versions of OpenShift.

4. List any affected packages or components.

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