Deprecate QuantumEngineSampler

[mpharrigan]

After much hand-wringing on #5361, I think we all have always agreed that QuantumEngineSampler needs to go.

• Deprecate this class in favor of ProcessorSampler.
  • remove without replacement: sampler interface that can send to one of many processor ids
  • remove without replacement: sampler interface that can accept cg.EngineProgram
  • keep if you really want to: use Engine.run() if you want to send to one of many processor ids
• Change cg.get_engine_sampler() and Engine.get_sampler() to delegate to Engine.get_processor(processor_id).get_sampler()
• There's a weird place in the cg.calibration tools that dispatches on QuantumEngineSampler to get an engine instance to call the run_calibrations method. Need to figure out what to do here. Likely: check if ProcessorSampler.processor.engine is not None or get rid of this option all together.