Support smart shuffle

[devgianlu]

This PR aims at adding support for Smart Shuffle. It is very early stages as some reverse engineering is required.

Spotify introduced the concept of signals and lenses. For Smart Shuffle we send a reset signal to the playlist with the enhance lense. The result is a list of ~310 tracks for a ~210 tracks playlist, but it is not clear where they should go. There is a suspicious metadata key called shuffle.distribution that may play a role in this. I have also noticed that the shuffle seed has been added to the session state.

There might be some refactoring required to handle the "injection" of tracks inside the current tracks list. Perhaps something similar to how the queue works?

[SuisChan]

The result is a list of ~310 tracks for a ~210 tracks playlist, but it is not clear where they should go. There is a suspicious metadata key called shuffle.distribution that may play a role in this.

According to my tests, signals returns a drop-in replacement playlist, where d(*) is the index in the queue by which tracks are played, every 10th is enhanced_recommendation, at least for me it is like that