Consider Webservice multiple deployments on checkDuplicateKeyFromEnv and gitlab.godebug.env

Summary

On !4331 (merged) we extended our checkDuplicateKeyFromEnv to consider root, local, global scopes. But as reported by an internal deployment, it failed to catch our webservice's chart multiple deployments mechanism, where multiple deployments could specify different extraEnv maps.

Steps to reproduce

We need to confirm, but in theory, these values:

gitlab:
  webservice:
    deployments:
      web:
        extraEnv:
          FOO: "BAR"
      websockets:
        extraEnv:
          GODEBUG: madvdontneed=1

It would, for the web deployment:

• checkDuplicateKeyFromEnv returns false (doesn't find GODEBUG)
• gitlab.godebug.env adds: GODEBUG: 'tlsmlkem=0,tlskyber=0'

And for the websockets deployment:

• checkDuplicateKeyFromEnv would still returns false (doesn't check deployment-level extraEnv)
• gitlab.godebug.env adds: GODEBUG: 'tlsmlkem=0,tlskyber=0'
• webservice.extraEnv also adds: GODEBUG: madvdontneed=1 which causes a duplication