pop() {
        try {
            while (this.#size) {
                const val = this.#valList[this.#head];
                this.#evict(true);
                if (this.#isBackgroundFetch(val)) {
                    if (val.__staleWhileFetching) {
                        return val.__staleWhileFetching;
                    }
                }
                else if (val !== undefined) {
                    return val;
                }
            }
        }
        finally {
            if (this.#hasDisposeAfter && this.#disposed) {
                const dt = this.#disposed;
                let task;
                while ((task = dt?.shift())) {
                    this.#disposeAfter?.(...task);
                }
            }
        }
    }
Evict the least recently used item, returning its value or
`undefined` if cache is empty.