blocks and labels representation

Hi !

Is it possible to write a schema so that the following representations are equivalent? (I looked at the way it is handled in Terraform, but I'm using another language so I would like to stick with something like `hcldec`).

```hcl
# terraform-like provisioning
provision "file" {
src = "foo"
dst = "/bar"
}

provision "exec" {
cmd = "/bar"
}
```

The label is used to internally tag the object with the `type` key, thus keeping the declaration order:

```json
{
"provision": [
{"type": "file", "src": "foo", "dst": "/bar"},
{"type": "exec", "cmd": "/bar"}
]
}
```

It would be a kind of enum-like block list.

Thanks !

Start by reviewing hcldec and Terraform's handling of blocks and labels. Determine whether a schema can represent the proposed enum-like block list while preserving declaration order, and use the equivalent HCL and JSON examples in the issue as the completion criteria.

Written by the indexing model from the issue text.