Refactor core interfaces

[iduartgomez]

Tracking issue for some internal refactoring we need to do. The goal is to:

• improve debugging capabilities over the kernel
• simplify and clean up some of the core code, cleaner abstractions
• improve certain error handling, ws api client/server comms, etc.
• add more testing around the boundaries of some components (like we did with handhsake handler, transport, etc.

Changes:

• move towards transactions executed end-to-end asynchronously instead of the current model of execution
  • wait for subtransactions results, communicate to ws client subscribers as network messages are inbound etc. and simplify overall the execution flow and reasoning (we essentially don't need to keep the state of the ops internally anymore in the OpManager)
• ... [TODO: add more detail]