Expose Elasticsearch Observation Interval in Helm Chart

[naemono]

relates to #5861

./bin/elastic-operator manager -h | grep observation
      --elasticsearch-observation-interval duration   Interval between observations of Elasticsearch health, non-positive values disable asynchronous observation (default 10s)

The above is a valid operator flag, but is not exposed within the config section of the values.yaml, and as such can only be adjusted via environment variable using the Helm Chart.

We should add:

Default value in values.yaml

config:
  elasticsearchObservationInterval: 10s

Section in templates/configmap.yaml

data:
  eck.yaml: |-
    elasticsearch-observation-interval: {{ .Values.config.elasticsearchObservationInterval }}