Fix extract method in trait outside the trait

[A4-Tacks]

Example

trait Foo {
    fn f(&self) -> i32;

    fn foo(&self) -> i32 {
        $0self.f()+self.f()$0
    }
}

Before this PR:

trait Foo {
    fn f(&self) -> i32;

    fn foo(&self) -> i32 {
        self.fun_name()
    }
}

fn $0fun_name(&self) -> i32 {
    self.f()+self.f()
}

After this PR:

trait Foo {
    fn f(&self) -> i32;

    fn foo(&self) -> i32 {
        self.fun_name()
    }

    fn $0fun_name(&self) -> i32 {
        self.f()+self.f()
    }
}

[flodiebold]

I'm not sure adding the method to the trait is usually going to be what the user wants?

[A4-Tacks]

I'm not sure adding the method to the trait is usually going to be what the user wants?

But it may be appropriate to do so instead of creating a generic function with all trait bounds and trait generic parameters

[Veykril]

I think in this case, when the selection contains self locals, we might want to offer both extract to function and extract to trait method? I do agree we can't assume that the user wants a trait function in this case