Allow service.enabled=false for deployment

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Currently the service is always enabled unless we deploy in "daemonset" mode:

opentelemetry-helm-charts/charts/opentelemetry-collector/templates/_helpers.tpl

Lines 134 to 145 in fce6cb4

	{{/*
	Compute Service creation on mode
	*/}}
	{{- define "opentelemetry-collector.serviceEnabled" }}
	{{- $serviceEnabled := true -}}
	{{- if and (eq .Values.mode "daemonset") (not .Values.service.enabled) }}
	{{- $serviceEnabled = false -}}
	{{- end }}
	{{- print $serviceEnabled }}
	{{- end -}}

I deploy a OpenTelemetry collector just for scraping Kubernetes cluster data:

presets:
  clusterMetrics:
    enabled: true
  kubernetesAttributes:
    enabled: true
  kubernetesEvents:
    enabled: true

I have all receivers disabled:

config:
  receivers:
    otlp: null
    jaeger: null
    zipkin: null

As far as I can tell, no ports need to be exposed in this setup. It would be nice if service.enabled=false would also disable the service object in this case.