Reproduction steps:
1. Go to song select
2. Open beatmap listing
3. Import a beatmap that would fit the current filter criteria
4. The count of visible beatmaps does not change
Fixed by updating the count on `BeatmapSetsChanged` too.
From a user's perspective, changing a sort / order mode shouldn't filter
away results, but we were doing this.
In terms of UX expectations, in stable this kind of scenario would
results in a group being added to the end of son select with "Not
ranked" or "Unknown". I think we should aim to match this eventually.