ChequeHandler, Scheduler and cmAccounts refactoring

[evlekht]

1. Introduce proper DI as required step for unit tests
   • Move some funcs to ChequeHandler or Processor.
   • Remove IdentificationHandler.
   • Abstract all cm-accounts interaction with CMAccounts service.
   • Abstract all cheque interaction with ChequeHandler.
   • Separate database for ChequeHandler and Scheduler
   • Make scheduler use mocked clock.
2. Reusable code for ASB:
   • Move some funcs to ChequeHandler
   • Move ChequeHandler from internal/messaging/ to pkg/chequehandler/. (no spaces is unfortunately required because of weird mockgen behavior.
   • Move Scheduler from internal/scheduler/ to pkg/scheduler/.
   • Remove timer from Scheduler, rework it to work with built-in timers and tickers.
   • Extract common sqlite database code to its own package.
3. Add mocks instead of noop implementations as preparation for unit tests.
4. Add unit-tests for scheduler.