[WIP] Add getter of minimal attributes necessary for pulse simulation in FakeBackendV2

[itoko]

Summary

Exceptionally add getter function of two custom attributes hamiltonian and u_channel_lo to FakeBackendV2. Those attributes are necessary for pulse simulation. They were in configuration() in BackendV1 but they disappear in BackendV2.

Details and comments

Currently, FakeManila().configuration().hamiltonian (u_channel_lo) returns Hamiltonian string (list of u channels info) while the counterpart FakeManilaV2().hamiltonian (u_channel_lo) fails with AttributeError. This commit enables to get those two attributes without failing by adding FakeBackendV2.__getattr__() function.

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[coveralls]

Pull Request Test Coverage Report for Build 2614734546

• 4 of 10 (40.0%) changed or added relevant lines in 1 file are covered.
• 205 unchanged lines in 14 files lost coverage.
• Overall coverage increased (+0.04%) to 83.992%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
qiskit/providers/fake_provider/fake_backend.py	4	10	40.0%

Files with Coverage Reduction	New Missed Lines	%
qiskit/exceptions.py	1	95.45%
qiskit/extensions/unitary.py	1	95.92%
qiskit/quantum_info/operators/symplectic/pauli_list.py	1	83.29%
qiskit/pulse/library/waveform.py	3	89.36%
qiskit/primitives/estimator.py	4	93.22%
qiskit/primitives/sampler.py	4	92.16%
qiskit/transpiler/passmanager.py	5	94.51%
qiskit/pulse/library/symbolic_pulses.py	6	94.69%
qiskit/qpy/interface.py	6	90.32%
qiskit/quantum_info/operators/symplectic/clifford.py	14	88.15%

Totals
Change from base Build 2546341916:	0.04%
Covered Lines:	55822
Relevant Lines:	66461

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💛 - Coveralls

[jakelishman]

With Aer having removed pulse simulation in Aer 0.13 and the deprecation/removal of pulse simulation from the fake backends in #11439 and #11442, I think this PR is obsolete now. I'll close it, but please feel free to re-open if there's more to discuss.