Detect imports/variables with mis-capitalization

I just spent a while debugging this error:

```
4 | asset_id::AssetID,
| ^^^^^^^ Could not find symbol "AssetID" in this scope.
```

Would be nice if the compiler was able to figure out that I probably meant `AssetId` instead of `AssetID`.

No file, test, or entry point is named. Start by locating the compiler diagnostic for unresolved imports or variables and trace how symbol suggestions are produced. Done means a missing `AssetID` can suggest `AssetId` when the matching import or variable differs only by capitalization, with coverage for the reported case.

Written by the indexing model from the issue text.