Improve Helm Chart Values Customization

[aveuiller]

Hello,

It's good to see that Vast CSI is going towards a Helm chart! I tried to use it and have a few improvements that would help a lot to integrate the image on a more generic way:

• We would like to use a custom Docker repository, it would be great to be able to customize it through the values files
• We would like to be able to load the username and password from a custom secret instead of storing them in the values files.

Thanks!