victoriametrics: support list values in args for duplicate CLI flags (e.g. multiple remoteWrite.url)

[djooberlee]

This pull request improves the handling of VictoriaMetrics configuration arguments, especially for cases where multiple values are needed for certain command-line flags. The changes allow users to specify lists of values in the pillar configuration, which are then correctly rendered as repeated arguments in the setup. Example usage is documented in the pillar file for vmagent.

Enhancements to argument handling:

• Updated the argument rendering logic in victoriametrics/_setup.sls to support lists of values, ensuring that each value is rendered as a separate command-line argument for flags that require repetition.

Documentation improvements:

• Added examples in victoriametrics/pillar.example under vmagent to show how to use lists for repeated arguments, such as multiple remoteWrite.url, remoteWrite.basicAuth.username, and remoteWrite.basicAuth.password values.