Move to Sampler V2

[nonhermitian]

backend.run() is being removed in favor of the Sampler interface. We will therefore need to move to that

[nonhermitian]

Looking into this, I see that things are not so great. Namely unlike backend.run doing this will require having the runtime as a dependency if passing a backend instance is still supported (which it should be).

Rather than passing a backend and a Batch or Session, I am leaning towards just allowing a Batch or Session to be passed in place of the current backend object and we can just add a Sampler job to the given container, if any, or do normal "job" mode if a backend is passed. I think I will return the job instance in all cases for reference.

[nonhermitian]

Closed by #216 but will be refactored in a follow-up since I think there is a better way