Qiskit / qiskit-ibm-runtime / 35870149582

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Alleviate fake_provider dependencies, move find_box_type outside it (#3367)

### Summary

Reduce the dependencies of the modules that contain the functionality
related to a primitive (`calibrator`, `executor`, `executor_sampler`,
`executor_estimator`, `noise_learner`, `noise_learner_v3`) on the
modules that contain local-mode constructs (`fake_runtime.*`).

The main mechanism is adding a `is_local` attribute to
`QiskitRuntimeService` and `QiskitRuntimeLocalService`, that allows
discerning between them at runtime without inspecting the instance.
Arguably such ability is needed (as we use those checks extensively),
and modelling it as an attribute has semantic value (we only have two
service classes currently, but they do have such distinction) and in
practice allows us to bypass the need to import them only for that
purpose.

With that in place, moving `find_box_type` closer to its main consumer
(`sampler.py`) became possible. There is still a non-ideal dependency
remaining (`run_quantum_program`, part of `fake_runtime`, depends on
`executor_sampler`), but seems less impactful (main scope of this PR is
the client-side primitives modularization).

### Details and comments

Related to #2749.

Related to a number of recent PRs:
* #3288 that made the dependency on `QiskitRuntimeLocalService` stronger
* #3334 where the dependency was made evident and `find_box_type` was
moved to avoid circular import issues (but placing domain logic in the
`fake_provider.*` module)
* #3346 that helped spotting the modules boundaries issue as a whole

### AI/LLM disclosure

- [x] I didn't use LLM tooling, or only used it privately.

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