Allow to use external redis service

[tossmilestone]

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Is your feature request related to a problem? Please describe.

Currently, Redis can only be deployed using the argocd-operator's own Redis service. In some scenarios where there is already an existing Redis service, we desire to be able to use the existing Redis service.

Describe the solution you'd like

1. The redis service could be disabled.
2. The argocd controllers support to be configured with other redis service.

Describe alternatives you've considered

None

Additional context

None