Fix automatic suggestion on `use_self`.
In an example like this:
```rust
impl Example {
fn fun_1() { }
fn fun_2() {
Example::fun_1();
}
}
```
Clippy tries to replace `Example::fun_1` with `Self`, loosing `::fun_1` in the process, it should rather try to replace `Example` with `Self`.
**Question**
- There may be other paths that need the same treatment, but I'm not sure I understand them fully:
- e648adf086/clippy_lints/src/use_self.rs (L94-L96)
- e648adf086/clippy_lints/src/use_self.rs (L225-L229)
a40d8e4479