feat(argocd-image-updater): Add ability to set .Values.namespaceOverride

[bradenwright]

I use this chart as a dependency but the .Release.Namespace is bootstrap, but I need to install argocd-image-updater chart into argo namespace. This allows that and makes everything fall into place for me.

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Checklist:

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

[mkilchhofer]

I really dislike the approach when charts install resources in namespaces outside the helm install --namespace xyz parameter.

Can you elaborate your use case a bit better? Do you use an umbrella chart which installs charts into multiple namespaces?

[mkilchhofer]

Did some research if there are charts in the world which supports exactly this behavior and I found a bunch:

• kubernetes/ingress-nginx
• metacontroller/metacontroller
• Some charts from Bitnami: https://github.com/search?q=repo%3Abitnami%2Fcharts%20namespaceOverride&type=code

I accept your PR now, thanks for your contribution 😎