feat(argo-cd): Add probes for Dex server >= 2.28.0

[pdrastil]

Add liveness and readiness probes for Dex server >= 2.28.0. For custom image tags where version cannot be determined are probes disabled by default

[mkilchhofer]

Hi @pdrastil can we reopen this?

I think we should use a simple solution for this and move all probes config to values.yaml
Something like this:

          {{- if .Values.dex.livenessProbe.enabled }}
          livenessProbe:
            {{- omit .Values.dex.livenessProbe "enabled" | toYaml | nindent 12 }}
          {{- end }}
          {{- if .Values.dex.readinessProbe.enabled }}
          readinessProbe:
            {{- omit .Values.dex.readinessProbe "enabled" | toYaml | nindent 12 }}
          {{- end }}

[pdrastil]

@mkilchhofer Sure I can reopen this with changes you've proposed.