Split Command interface into smaller interfaces

[wesen]

Command currently consists of the following methods:

type Command interface {
	Run(
		ctx context.Context,
		parsedLayers map[string]*layers.ParsedParameterLayer,
		ps map[string]interface{},
		gp Processor,
	) error
	Description() *CommandDescription
}

However, this tightly couples the Description() abstraction, which is very useful on its own, from the Run() execution type. It makes sense to split out these interfaces into:

• RunIntoGlazeProcessor
• RunIntoWriter (for plain byte / string output)
• Run (for just executing)
• RunIntoStruct[T] generic which can be useful for chaining

These could potentially be extended for HTML runners, etc...