SCORU, PVM: Add ability to the PVM to consume messages incrementally

Currently, PVM works in two main phases:

• Collection: when messages are being accumulated to the input buffer
• Evaluation: when those messages are being processed by the kernel

Collection lasts between SoL and corresponding EoL, then Evaluation starts.

For the purpose of the sequencer this behavior should be extended, and Evaluation phase should be forced by a PVM method invocation, in order to react to incremental addition of the messages to maintain corresponding PVM state, which will be exposed to the user as optimistic state.