Support for setting kubectl parallelism limit in the Operator

As a user of OpenShift GitOps, my application controller gets OOM killed for no obvious reasons at startup. I can observe a huge memory spike on startup. This probably is due to the same issue as observed in https://github.com/argoproj/argo-cd/issues/5505 (where they run vanilla Argo CD against OCP).

As a consequence, I want a sane default for the application controller's kubectl parallelism limit (--kubectl-parallelism-limit - see https://argo-cd.readthedocs.io/en/stable/operator-manual/server-commands/argocd-application-controller/#options

This limit should be set to the value 10

Additionally, if I decide that I want to increase this limit, I should have the option in the CR to do so.

This should go into a patch release of v1.2 in the following release branches.

https://github.com/redhat-developer/gitops-operator/tree/v1.2

https://github.com/argoproj-labs/argocd-operator/tree/rhos-v1.2

Acceptance criteria:

• The flag --kubectl-parallelism-limit for the application controller is set to 10 by default
• This value can be overridden by specifying a number for .spec.controller.kubeParallelismLimit in the ArgoCD CR spec