TypePath of types inside functions do not include the function name.

Deriving `TypePath` on a type does not include functions it is nested within. This could result in unexpected type paths, and even matching type paths for two distinct types.

Here is a test that demonstrates the issue.

```rust
#[test]
fn types_in_functions_dont_overlap() {
#[derive(TypePath)]
struct MyType;

fn nested(super_type_path: &str) {
#[derive(TypePath)]
struct MyType;

assert_ne!(::type_path(), super_type_path);
}

nested(::type_path());
}
```

Start by running the supplied Rust test and tracing the TypePath derive implementation. Check how paths are generated for the outer and nested MyType definitions; done means the two type_path() values are distinct and the nested path includes its enclosing function name.

Written by the indexing model from the issue text.