src/vs/base/common/collections.ts/diffMaps
export function diffMaps<K, V>(before: Map<K, V>, after: Map<K, V>): { removed: V[], added: V[] } {
	const removed: V[] = [];
	const added: V[] = [];
	for (let [index, value] of before) {
		if (!after.has(index)) {
			removed.push(value);
		}
	}
	for (let [index, value] of after) {
		if (!before.has(index)) {
			added.push(value);
		}
	}
	return { removed, added };
}