HelmRepository should support different OCI Providers

Feature Request

Why

The Helm Repos defined in the values.yaml should have a parameter to set the provider for HelmRepository resources. This gives the ability for flux to use OIDC credentials. The usecase I am using this for is to pull OCI helm charts from ECR. This will also be useful for other cloud providers other than AWS. IRSA credentials can be tied to the helm flux pod, to pull the OCI chart. In this scenario, neither a un/pw or an existing secret is needed.

https://fluxcd.io/flux/components/source/helmrepositories

Proposed Solution

Adding the needed variable, and allow not setting un/pw or a external secrets.