Story:

Implement the logic in the MCO controller to read and parse the new map format of the machine-config-osimageurl ConfigMap. The controller must be able to identify the available streams and select the default stream when the user does not specify a different one in the MachineConfigPool CR.

Acceptance Criteria:

1. The MCO correctly parses the ConfigMap with the map format.
2. The operator correctly identifies the URL associated with the default stream.
3. The already in place redering logic continues to work and always consumes the default stream.
4. The logic is covered by unit tests.