Add auto trait name for generate_trait_from_impl

[A4-Tacks]

Auto generate trait name from first method.

Input:

impl S$0 {
    fn foo() {}
}

Old output:

trait NewTrait {
    fn foo();
}

impl NewTrait for S {
    fn foo() {}
}

This PR output:

trait Foo {
    fn foo();
}

impl Foo for S {
    fn foo() {}
}

[ChayimFriedman2]

Why specifically from the first method, or from methods at all? I'm not sure this is advantageous.

[A4-Tacks]

Having placeholder snippet group, incorrect name is irrelevant