SoundPlayer: Implement playlist shuffle mode

The shuffling algorithm uses a naïve bloom filter to provide random
uniformity, avoiding items that were recently played.  With 32 bits,
double hashing, and an error rate of ~10%, this bloom filter should
be able to hold around ~16 keys, which should be sufficient to give the
illusion of fairness to the shuffling algorithm.

This avoids having to shuffle the playlist itself (user might have
spent quite a bit of time to sort them, so it's not a good idea to mess
with it), or having to create a proxy model that shuffles (that could
potentially use quite a bit of memory).

Userland/Applications/SoundPlayer/Player.cpp

@@ -92,6 +92,15 @@ void Player::set_volume(double volume)
     volume_changed(m_volume);
 }
 
+void Player::set_shuffle_mode(ShuffleMode mode)
+{
+    if (m_shuffle_mode != mode) {
+        m_shuffle_mode = mode;
+        m_playlist.set_shuffling(mode == ShuffleMode::Shuffling);
+        shuffle_mode_changed(mode);
+    }
+}
+
 void Player::play()
 {
     m_playback_manager.play();