Client provided `id` handling changes

**Is your feature request related to a problem? Please describe.**

# Allow `id` field to be set _outside_ the `attributes` object.

In the main API I operate, idempotence on create is handled by just setting the `id` of the resource. It's one of the joys of using UUIDs. Ash currently works with this:

```json
{
"data": {
"attributes": {
"id": "d67fc7b1-24d1-4c3a-9129-97ece194cbc8"
}
}
}
```

But not this:

```json
{
"data": {
"id": "d67fc7b1-24d1-4c3a-9129-97ece194cbc8"
}
```

**Describe the solution you'd like**

Simply accept `id` as a direct child of `data`. (I would say if the client provided it in two spots, an error is returned rather than argue about which has precedence.)

**Express the feature either with a change to resource syntax, or with a change to the resource interface**

Accepting IDs shouldn't require any actual DSL unless you wanted to support returning errors on `id` being a direct child of `data`.

No file or test is named in the issue. Start by locating the JSON:API create-payload handling and the existing path for an id inside attributes; the work is done when a direct data id is accepted and supplying ids in both locations returns an error, with coverage for these cases.

Written by the indexing model from the issue text.