[Enhancement][opensearch] Add the seedHosts and initialMasterNodes parameters to flexibly set the discovery.seed_hosts and cluster.initial_master_nodes settings.

[nutslove]

Is your feature request related to a problem? Please describe.
We would like to set cluster.initial_master_nodes and discovery.seed_hosts directly from Values.
Currently, in the statefulset.yaml template, cluster.initial_master_nodes and discovery.seed_hosts cannot be set flexibly.
We are trying to build an OpenSearch cluster across three different Kubernetes(OpenShift) clusters for certain reasons.
※We plan to deploy one master, one data, and one ingest node (pod) per Kubernetes(OpenShift) cluster.
Therefore, we would like to modify cluster.initial_master_nodes and discovery.seed_hosts from values.

Describe the solution you'd like
Add an if condition to allow setting cluster.initial_master_nodes and discovery.seed_hosts in the statefulset.yaml template if initialMasterNodes and seedHosts exist in values, like the example below:

        {{- if (and (has "master" .Values.roles) (not .Values.singleNode)) }}
        - name: cluster.initial_master_nodes
        {{- if .Values.initialMasterNodes }}
          value: "{{ .Values.initialMasterNodes }}"
        {{- else }}
          value: "{{ template "opensearch.endpoints" . }}"
        {{- end }}
        {{- end }}
        - name: discovery.seed_hosts
        {{- if .Values.seedHosts }}
          value: "{{ .Values.seedHosts }}"
        {{- else }}
          value: "{{ template "opensearch.masterService" . }}-headless"
        {{- end }}

Thank you for your time.

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