Support migration to Azure Managed Identity

1. Proposed title of this feature request

Support migration to Azure Managed Identity

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

Many customers would like to migrate to Azure Managed Identity but have numerous existing clusters and an aversion to supporting two concurrent operational requirements. Therefore they would like to migrate existing Azure clusters to Managed Identity in a safe manner after they have been upgraded to a version of OCP supporting that feature (4.14+).

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

• Provide a uniform operational experience for all clusters running versions which support Azure Managed Identity without having to decommission long running clusters

4. List any affected packages or components

Potentially all components which were part of OCPSTRAT-506