0.12: refactors

Changes include:

• New type alias Agent that is returned from init_agent
• system prompt now includes more granular information about dependencies
• extract out debug_call_counter.rs
• extract out update_pointers.rs
• rename Runtime::init to Runtime::new
• extract out profile.rs
• ensure evolve future is Send, which involved not holding syn::File across await points and dropping async from the compile function