[Feature] "offline" metadata for docs

### Is this a new bug in dbt-core?

- [x] I believe this is a new bug in dbt-core
- [x] I have searched the existing issues, and I could not find an existing issue for this bug

### Current Behavior

When setting the property `type` for a column, `dbt` raises a warning `CustomKeyInObjectDeprecation`.
I'm guessing this is because it is expecting us to use the key `data_type`.

However, when using `dbt docs generate`, `data_type` results in blank column types, while `type` populates them correctly.

### Expected Behavior

Ideally, both keys would be merged into a single one that does not trigger this warning.
I'm guessing `data_type` is the intended one moving forward, since that is what's used when enforcing model contracts.

### Steps To Reproduce

```
models:
- name: my_model
columns:
- name: "{{ var('timestamp_table_uuid_column') }}"
description: "{{ doc('uuid') }}"
type: string
data_type: string
```

### Relevant log output

```shell

```

### Environment

```markdown
Core:
- installed: 1.11.2
- latest: 1.11.2 - Up to date!

Plugins:
- bigquery: 1.11.0 - Up to date!
```

### Which database adapter are you using with dbt?

bigquery

### Additional Context

_No response_