helm: Fix in-cluster remote URLs when gateway and nginx are disabled

[kimxogus]

What this PR does

Current mimir-distributed helm chart creates in-cluster remote urls nginx service's cluster url even when nginx is disabled.

• mimir/operations/helm/charts/mimir-distributed/templates/_helpers.tpl

  Lines 37 to 43 in 9144986

  	{{- define "mimir.gatewayUrl" -}}
  	{{- if eq (include "mimir.gateway.isEnabled" . ) "true" -}}
  	http://{{ include "mimir.gateway.service.name" . }}.{{ .Release.Namespace }}.svc:{{ .Values.gateway.service.port | default (include "mimir.serverHttpListenPort" . ) }}
  	{{- else -}}
  	http://{{ template "mimir.fullname" . }}-nginx.{{ .Release.Namespace }}.svc:{{ .Values.nginx.service.port }}
  	{{- end -}}
  	{{- end -}}

• https://github.com/grafana/mimir/blob/9144986d6b9a662508b44a07884d46dc2f3da73a/operations/helm/charts/mimir-distributed/templates/_helpers.tpl#L551-557

This PR fixes this behavior. mimir.remoteWriteUrl.inCluster and mimir.remoteReadUrl.inCluster will be query-frontend and distributor's url when both gateway and nginx are disabled.

Which issue(s) this PR fixes or relates to

none

Checklist

• Tests updated.
• Documentation added.
• CHANGELOG.md updated - the order of entries should be [CHANGE], [FEATURE], [ENHANCEMENT], [BUGFIX].
• about-versioning.md updated with experimental features.

[narqo]

Looks good to me. Thank you for fixing it.