Add select stmts support for replace_let_with_if_let

[A4-Tacks]

• And migrate edit_in_place::Indent into edit::AstNodeEdit

Example

enum E<T> { X(T), Y(T) }

fn main() {
    $0let x = E::X(92);
    let y = x;$0
    let _ = ();
}

Before this PR

enum E<T> { X(T), Y(T) }

fn main() {
    if let x = E::X(92) {
    }
    let y = x;
    let _ = ();
}

After this PR

enum E<T> { X(T), Y(T) }

fn main() {
    if let x = E::X(92) {
        let y = x;
    }
    let _ = ();
}