Fix expand rest pattern in tuple and slice pattern

[A4-Tacks]

Assist: expand_tuple_rest_pattern

Fills fields by replacing rest pattern in tuple patterns.

Example

fn foo(bar: (char, i32, i32)) {
    let (ch, ..$0) = bar;
}

->

fn foo(bar: (char, i32, i32)) {
    let (ch, _1, _2) = bar;
}

---

Assist: expand_slice_rest_pattern

Fills fields by replacing rest pattern in slice patterns.

Example

fn foo(bar: [i32; 3]) {
    let [first, ..$0] = bar;
}

->

fn foo(bar: [i32; 3]) {
    let [first, _1, _2] = bar;
}