feat: Made ng labels env driven (#6438)

* feat: Adds karpenter ng to list of ng constants

* feat: made nodelabels env driven

* feat: Updates env get as per repo standards

* prom client in chart-sync

* fix in yaml

* chore: resolve merge conflict

* APP_SYNC_SHUTDOWN_WAIT_DURATION env

* code cleaning

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Co-authored-by: prakhar katiyar <prkhrkat@gmail.com>

Author: abhibhaw