Convert Runner class into interface

[warownia1]

All non-abstract methods of Runner should be extracted to the Scheduler or its helper classes. Runners should not contain any logic other than that needed to communicate with an underlying queuing system. This change will improve testability and unclutter the code by utilizing modularity and object composition over inheritance.

Runner:
  + submit(args: List[str], cwd: str) -> str
  + status(job: JobMetadata) -> JobStatus
  + cancel(job: JobMetadata)

Each method should have a batch_* variant with default implementation.

[warownia1]

Advantaged of separation and composition over inheritance are:

• cleaner custom runner creation by removing all parts which are not involved in communication with the execution system
• easier testing of each component in isolation
• less redundancy, runner and command line builder need to be tested once for all types of runners

New runner can be composed of the following components: command line builder (this opens a possibility to have a dedicated builder for windows), execution manager interface implementing submit, check_status, cancel, release/free methods, main logic gluing the components together.