[BUG] No column level auto-complete in vscode

Issue was originally opened as FEAT. But, the vscode extension clearly describes column auto-completion as a supported feature. So I have updated the issue to BUG.

**Is your feature request related to a particular component of the dbt Fusion Engine**
- [ ] CLI Features
- [ ] Adapter or Database Driver Features
- [ ] SQL Understanding Features
- [x] VS Code extension

**Describe the solution you'd like**

With dbt fusion, vscode "knows" the shape of objects (CTEs, tables, views...) that I'm referencing in my SELECT statement.

Yet, I still have to type out every column name myself. Vscode never tries to help with that.

No matter what I try, the suggestions are always SQL functions.

I actually thought (perhaps wrongly) that the official dbt extension already supports column-level autocomplete. But that doesn't seem to be the case.

Can support be added?

Toy example:

```sql
WITH foo AS (
SELECT column1 AS colour
FROM (VALUES ('a'))
)
SELECT
*
FROM foo
```

Mouseover `*` to prove that vscode knows the shape of `foo`:

Start typing a column name, and observe no relevant autocomplete: