Features from optional dependencies

actix-rt implicit feature

Enables actix-rt

actix-rt:

Tokio-based single-threaded async runtime for the Actix ecosystem

Affects cleanup::actixrt, cleanup::start_cleaner

tokio implicit feature

Enables tokio

tokio:

An event-driven, non-blocking I/O platform for writing asynchronous I/O backed applications

Affects cleanup::start_cleaner