[influxdb] Support configurable StatefulSet labels/annotations

[lovetoburnswhen]

Adds the statefulSetAnnotations/statefulSetLabels properties to values.yaml to allow users to specify custom labels and annotations on the resulting StatefulSets.

This feature would be tremendously useful for environments that require certain labels to be set - the only alternative would be to fork the chart internally.

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Tested with:

❯ helm template ./charts/influxdb -s templates/statefulset.yaml --set 'statefulSetLabels.foo=bar' --set 'statefulSetAnnotations.bar=baz'      
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# Source: influxdb/templates/statefulset.yaml
apiVersion: apps/v1
kind: StatefulSet
metadata:
  name: release-name-influxdb
  labels:
    helm.sh/chart: influxdb-4.12.6
    app.kubernetes.io/name: influxdb
    app.kubernetes.io/instance: release-name
    app.kubernetes.io/version: "1.8.10"
    app.kubernetes.io/managed-by: Helm
    foo: bar
  annotations:
    bar: baz

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• [ ] CHANGELOG.md updated None found
• [x] Rebased/mergable
• [x] Tests pass
• [x] Sign CLA (if not already signed)