fix(polka-storage-server): Have NodeType hold needed values

[aidan46]

I feel that we could turn this abstraction around and make the NodeType contain the necessary state for the respective node type.

This would make weird configs unrepresentable and avoid the Option<PeerId>

Originally posted by @jmg-duarte in #666 (comment)

[aidan46]

There is an issue with having the NodeType hold the CLI config values. The reason is that ValueEnum is made for unit-type enums, and implementing ValueEnum is possible but makes the CLI very messy. Here is a stackoverflow thread about the same thing. We can do two things if we want this to work:

1. Get rid of the CLI arguments that are not the key or the config file
2. Have a different NodeType for config vs CLI argument, where the latter stays a unit-type enum. This would also mean having 2 different config structs (currently we deserialise to ConfigurationArgs if it is TOML or YAML).