Bugfix for missing qubit property

[nkanazawa1989]

Summary

With #11095 handling for the missing qubit property was gone. This PR readds the handling for partly missing qubit property with a unit test.

Details and comments

When some qubit doesn't report qubit properties (i.e. T1, T2, frequency), the convert_to_target function crashes during the conversion of BackendV1 into V2 model.

[qiskit-bot]

One or more of the the following people are requested to review this:

• @Qiskit/terra-core

[coveralls]

Pull Request Test Coverage Report for Build 8043950737

Details

• -2 of 7 (71.43%) changed or added relevant lines in 1 file are covered.
• 37 unchanged lines in 2 files lost coverage.
• Overall coverage decreased (-0.05%) to 89.249%

---

Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
qiskit/providers/backend_compat.py	5	7	71.43%

Files with Coverage Reduction	New Missed Lines	%
crates/qasm2/src/lex.rs	7	91.44%
crates/qasm2/src/parse.rs	30	95.77%

Totals
Change from base Build 8023329404:	-0.05%
Covered Lines:	58877
Relevant Lines:	65969

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💛 - Coveralls

[mtreinish]

LGTM, thanks for fixing this.

[mtreinish]

FWIW, looking at the target code:

qiskit/qiskit/transpiler/target.py

Lines 318 to 326 in 945fe1d

	if qubit_properties is not None:
	if not self.num_qubits:
	self.num_qubits = len(qubit_properties)
	else:
	if self.num_qubits != len(qubit_properties):
	raise ValueError(
	"The value of num_qubits specified does not match the "
	"length of the input qubit_properties list"
	)

so not filtering faulty qubits is the expected behavior here. If the number of qubits in the properties dict differs from the number of qubits on the backend it'll error.