Allow custom args on deployment spec

[thiagosalvatore]

Description

Enables support for custom args on deployment spec. The current helm only allows custom commands, making it hard to reuse the image by changing the args only and keeping the command (ENTRYPOINT).
It is supported by Kubernetes, for reference: https://kubernetes.io/docs/tasks/inject-data-application/define-command-argument-container/#use-environment-variables-to-define-arguments.

Gist with template tests

Implements #142

TODOs

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• Update the docs.
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Release Notes (draft)

Added / Removed / Updated [X].

[X] - Added new input parameter containerArgs that can be used to define custom args that should be passed to the deployment spec. It behaves exactly as the containerCommand, the only difference is that it will populate the args instead of the command in the spec.

[autero1]

Thanks for the PR @thiagosalvatore !
The change LGTM, running the tests now.