remove actors

[OlegYch]

there isn't much reason to use actor model in this kind of application and there is a bunch of hard to debug issues outstanding currently which are caused by its use

[vincenzobaz]

Given that scastie is pretty resource intensive, I think that akka could be useful to distribute workers across multiple machine with its cluster module. I think upgrading to Akka Typed would help debug issues and make the code more clear...