Deprecate and remove support for .spec.initialRepositories & spec.repositoryCredentials

[svghadi]

Is your feature request related to a problem? Please describe.
Support for repo configs in argocd-cm is already deprecated in upstream and planned(argoproj/argo-cd#19768) to be removed in Argo CD v3.0. Operator supports this upstream feature via .spec.initialRepositories & spec.repositoryCredentials fields in ArgoCD CR.

• https://argocd-operator.readthedocs.io/en/latest/reference/argocd/#repository-credentials-example
• https://argocd-operator.readthedocs.io/en/latest/reference/argocd/#initial-repositories

Describe the solution you'd like
Deprecate these fields in the ArgoCD CRD and plan their removal according to the upstream timeline.

Open Question
Do we want to continue supporting these fields in the operator by using a different internal mechanism to create the required repos and repo credentials in Argo CD?