higher_order.js: create wrapped versions of promise generator functions

higher_order.js

// produce a wrapped promise generator whose promises regenerate instead of rejecting
export function retrying(func, n=Infinity) {
	return n == 1
		? func
		: () => func().catch(retrying(func, n - 1));
}

// produce a wrapped promise generator whose promises ignore rejections
export function noreject(func) {
	return () => func().catch(() => {});
}