Add transaction handler support to the processor

[maht0rz]

Is your feature request related to a problem? Please describe. As of now the processor only supports processing of unproven blocks. It would be nice to introduce a transaction handler as well.

Describe the solution you'd like Introduce an additional transactions handler for the processor - possibly with the ability to specify handlers per concrete runtime method - cross type checked with the concrete AppChain runtime.

Describe alternatives you've considered N/A

Additional context N/A