fix: assign bindings in irrefutable let-else or-patterns

[ivov]

let else in combination with or-patterns with an irrefutable alternative now assign the subject to the bindings instead of leaving them at Go zero values. The whole let cannot fail, but the bindings still need to receive the value.

fn main() {
  let x | x = 42 else {
    return
  }
  fmt.Println(x)
}

Previously printed 0 but now prints 42.

[github-actions]

Released in lisette-v0.2.1