Update comments that reference refactored symbols  #12583

In vscode, you can click F2 to rename a module item. In some cases, the module item is referenced with square brackets in one of the comments. For example

// ... some where in your crate
//! This module uses [Builder] to do foo.


// ... else where
struct Builder {
 input_path: PathBuf,
 output_path: PathBuf
}

Later you decide to refactor Builder, for example, by giving it a more special name. You would want the comments that reference the Builder to be refactored, ideally. It would be nice for Rust-Analyzer to locate and update those references and update them when the code is refactored.