New lint: Detect Ok(foo?) patterns and suggest .map_err(From::from) instead.

When I started writing Rust code I used to do the following pattern to convert Result types. Turns out I am not the only one doing it, and I think it's fairly common. When I learned more about the From and Into traits I noticed .map_err(From::from) could be used instead which seems cleaner.

So instead of writing this:

fn bar() -> Result<File, MyError> {
    Ok(File::open("foo.txt")?)
}

It could suggest this:

fn bar() -> Result<File, MyError> {
   File::open("foo.txt").map_err(From::from)
}

No source file or test entry point is named. Start by reviewing Clippy's existing lint implementations and how Rust handles Result expressions with ?; done means detecting the shown Ok(foo?) pattern and suggesting the equivalent .map_err(From::from) form without changing other cases.