add new opster job label to securityconfig-update job and pod

[monotek]

Description

• add new opster.io/opensearch-job label to securityconfig-update job and pod
• did not use existing opster.io/opensearch-cluster label because it's used as selector by the service

Issues Resolved

• makes it easier for tools like kyverno to exclude certain cluster policies by label

Check List

• Commits are signed per the DCO using --signoff
• Unittest added for the new/changed functionality and all unit tests are successful
• Customer-visible features documented
• No linter warnings (make lint)

If CRDs are changed:

• CRD YAMLs updated (make manifests) and also copied into the helm chart
• Changes to CRDs documented

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