we have a number of methods of the form init_x_connection, which makes a connection to an external service (postgres, redis, etc).

However, the method init_timescale_connection is actually creating a listenstore class, and isn't directly related to the timescale database connection (this is done in listenbrainz.db.timescale.init_db_connection instead).

We should rename init_timescale_connection and make it clear that this is making a ListenStore instead.

The redis listen store is similarly named.

Bonus points for making it a flask extension as well