Improve span information for expanded types

Modules which look like:

```wasm
(module
(import "" "" (func))
)
```

get automatically expanded to:

```wasm
(module
(type (func))
(import "" "" (func (type 0)))
)
```

During the expansion process for doing this, though, insertion of the new `(type ...)` uses `Span::from_offset(0)` for much of its span information. The reason for this is that the `TypeUse` here specifically doesn't have a span within `FunctionType` and namely in the example above there's nothing to assign the span to (ideally it's sort of `func`). This is also the case with the component model for:

```wasm
(component
(type (option (list u8)))
)
```

getting expanded to

```wasm
(component
(type (list u8))
(type (option 0))
)
```

Here though we don't keep track of the span of the `list` keyword and otherwise there isn't great span information to insert.

I don't know really how important this is to fix. I don't think it's actually possible to get any errors which use these spans, so it could be entirely benign to leave all these spans as 0. I still feel though that it would probably be best to figure out a good way to thread through a proper span here.