General

The image registry would get Azure credentials using Azure SDK's generic NewDefaultAzureCredential function. 

Why is this important?

• Different OpenShift components implement different patterns of setting up environment variables to get Azure credentials for different Azure authentication methods.
• Refactoring the pattern to use `NewDefaultAzureCredential` will enable OpenShift components to have the same pattern in setting up Azure credentials
• This is also needed to enable authentication with Service Principal with backing certificates for ARO HCP.

Acceptance Criteria

• Refactored code that uses `NewDefaultAzureCredential`
• Updated documentation
• ARO HCP CI coverage

Dependencies (internal and external)

Azure SDK

Done Checklist

CI - Existing CI is running, tests are automated and merged.
CI - AKS CI is running, tests are automated and merged.
DEV - Upstream code and tests merged: <link to meaningful PR or GitHub Issue>
DEV - Upstream documentation merged: <link to meaningful PR or GitHub Issue>
DEV - Downstream build attached to advisory: <link to errata>
QE - Test plans in Polarion: <link or reference to Polarion>
QE - Automated tests merged: <link or reference to automated tests>
DOC - Downstream documentation merged: <link to meaningful PR>