Add logs about duration of SDK initialization

[varsill]

This PR:

• moves Agora SDK initialization from handle_setup to handle_playing
• renames modules in lib/ according to the assumed naming convention in the membrane plugins
• adds logs about the duration of Agora SDK initialization

[nickdichev-firework]

Sweet, I've also seen that there is some data about the sdk initialization that we can get from the agora side. I wonder if we would be able to see anything interesting

[varsill]

@nickdichev-firework Definitely we should be able to find something interesting! We would need to find those logs for the channel which was used during the session for which startup took that long