Has method includes expired keys

[hongkuancn]

I noticed the Has method will print true when checking an expired key

func Test_Has(t *testing.T) {
	cache := New[int, int]()
	cache.Set(1, 1, time.Nanosecond)
	time.Sleep(time.Second)
	fmt.Println(cache.Has(1))
}

output:

true

I think it makes more sense to exclude expired keys here and it won't cause much overhead just to check if the item expires. If so, I have some time to make the change.

[swithek]

I believe most data/status retrieval methods include expired keys (i.e., Len(), Keys(), Range(), Has()), so we should probably update all of them. Using item.isExpiredUnsafe() in them, just like you did in your latest PR, should be enough.

If you can tackle this issue, feel free to do that, I'll review your PRs ASAP.