Incorrect downlevel compilation for block scoped bindings captured in class initializers

[vladima]

let ar = [];
for (let i = 0; i < 2; i++) {
  ar.push(class { x = i; });
}
console.log(new ar[0]().x); // should this be 0, now prints 2
console.log(new ar[1]().x); // should this be 1, now prints 2

[jakebailey]

Just looking at old issues; this one is the same as #8578 and was also fixed by #43197.