Check custom values working when chart fetched from an OCI repository.

[absoludity]

Describe the bug
On #6223 (comment) , @overag3 identified and tested an issue with the custom values not working when using Harbor, in their case, but specifically, Harbor with OCI storage.

Our verification of this feature (custom values) has only ever been done with the non-oci packaging, so it is possible that the same path is not followed with OCI (though there's no reason why we shouldn't).

To Reproduce

We need to reproduce this to verify and fix.

1. Package a chart with an additional values-custom.yaml in both chartmuseum and an OCI repo,
2. Check for the custom values being used in both.

Expected behavior

Custom values should be displayed in the UX for both.