Convert responseErrors cache to an LRU cache

[n-peugnet]

This should not be too hard to do. Given it is currently a FIFO one, it is implemented with a simply linked list. We wilk have to use a doubly linked list instead to be able to move the elements.

flarum-ext-cross-references/js/src/forum/cache.ts

Line 80 in aa2d400

private static responseErrors: Cache<boolean> = new FIFOCache(128);