Requests to improve documentation for plugin developers

#### Description

I am writing a Plugin for the first time and I have several questions that I have not found answers for in the [developer docs](https://developer.hashicorp.com/packer/docs/plugins/creation/custom-builders). I'm hoping to list out my questions in a plain way to give yall ideas on to potentially improve the docs. Any short form answers you have would also be welcome in this issue :pray:

- [ ] Should I pass values using `state` or as [parameters to individual builder](https://github.com/hashicorp/packer-plugin-vmware/blob/main/builder/vmware/iso/builder.go#L60) `Step`?
- [ ] Examples of annotations available for Config parameters (`required`... `default` )?
- [ ] Should saving an artifact be baked into the build (like AWS AMIs) or as a postprocessor (docker uses a post processor)? What are the +/- of these approaches? I kind of prefer the docker implementation but I haven't seen that anywhere else
- [ ] When does a `cleanup` step run? during step? What if `multistep.ActionHalt` is returned? Is there a global cleanup function for after all steps are completed?
- [ ] Advice on error handling regarding `ui`
- [ ] Docs on writing acceptance tests