Invalid Registry in Credentials

### What happened?
KCLInput credentials with a url, username and password fail in v0.12.2 with "Invalid registry ". This worked for v0.12.1 and all versions below to v0.11.2 (the last version I've been using for over a year now).

I was attempting to test out new OCI cache behaviour introduced in v0.12.3 (#282) but the function failed to load my usual OCIs. No other environment changes. So I iterated a version of function-kcl from v0.11.2 upwards until this failure occurs, and it hits at v0.12.2.

### How can we reproduce it?
Use v0.12.2 or the latest v0.12.3 and attempt to source from an oci url to Azure Container Registry using a username/password with registry pull permissions:

Relevant part of composition:
```
- functionRef:
name: kcl-function
input:
apiVersion: krm.kcl.dev/v1alpha1
kind: KCLInput
metadata:
name: basic
spec:
credentials:
password:
url: https://.azurecr.io
username:
source: oci://.azurecr.io/?tag=
```

### What environment did it happen in?
Function version: v0.12.2+

Kind cluster running:
Client Version: v1.29.1
Kustomize Version: v5.0.4-0.20230601165947-6ce0bf390ce3
Server Version: v1.35.5

Reproduce the failure with the shown KCLInput credentials and Azure Container Registry source, comparing v0.12.1 with v0.12.2 or v0.12.3. Trace the credential and OCI registry handling from the KCLInput entry point; done means authenticated Azure Container Registry sources load successfully without the Invalid registry error.

Written by the indexing model from the issue text.