Simplify id & remove resource fields

[fornellas]

All resource types must have both an "id" field, that uniquely identifies the resource at a host, and a "remove" field, to inform whether it should be... removed.

As of now, both fields are mandatory, but they can live anywhere in the struct, and the Id field, requires a special tag.

This PR simplifies that, enforcing instead that all resources have the first 2 fields as such:

type Foo struct {
FooName string `yaml:"foo_name"`
Remove bool `yaml:"remove,omitempty"`
}

which simplifies things quite a bit.

In particular, when marshaling yamls, the id field will be guaranteed to be the first one, which eases understanding.

---

Stack:

• Add apply command #116
• Add plan command #107
• Add internal/plan #108
• Add Blueprint tests #111
• Add Step tests #110
• Change 'remove' to 'absent' #109
• Resources: Add Satisfies #106
• Simplify id & remove resource fields #105 ⬅

⚠️ Part of a stack created by spr. Do not merge manually using the UI - doing so may have unexpected results.