feat(argo-workflows): Support array of strings in argo-workflows image pull secrets

[CiprianAnton]

There are helm charts that expose image pull secrets as an array of strings. Argo Workflows helm exposes them as an array of objects {name: value}.

Add support to define image pull secrets as string, for better interoperability with other helm charts. This way, the same imagePullSecrets can be passed to multiple helms. Backwards compatibility is mantained.

Tested the behavior with running helm template. Compared the original and modified templates, and they are as expected.

The effect is shown bellow for the following input:

images:
  pullSecrets:
    - name: pullSecretNameAsObject
    - pullSecretNameAsString

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Checklist:

• [x] I have bumped the chart version according to versioning
• [x] I have updated the documentation according to documentation
• [x] I have updated the chart changelog with all the changes that come with this pull request according to changelog.
• [x] Any new values are backwards compatible and/or have sensible default.
• [x] I have signed off all my commits as required by DCO.
• [ ] My build is green (troubleshooting builds).

Changes are automatically published when merged to main. They are not published on branches.