Fix a corner case of SparsePauliOp.apply_layout

[t-imamichi]

Summary

SparsePauliOp.apply_layout raises an error if a zero-qubit operator is given.
This PR fixes the case.

from qiskit.quantum_info import SparsePauliOp

op = SparsePauliOp("")
print(op.apply_layout(None, 3))

main branch

SparsePauliOp([''],
              coeffs=[1.+0.j])
Traceback (most recent call last):
  File "/Users/ima/tasks/4_2024/qiskit/terra/tmp/layout.py", line 5, in <module>
    print(op.apply_layout(None, 3))
  File "/Users/ima/tasks/4_2024/qiskit/terra/qiskit/quantum_info/operators/symplectic/sparse_pauli_op.py", line 1167, in apply_layout
    return new_op.compose(self, qargs=layout)
  File "/Users/ima/tasks/4_2024/qiskit/terra/qiskit/quantum_info/operators/symplectic/sparse_pauli_op.py", line 349, in compose
    q = np.logical_and(z1[:, np.newaxis], x2).reshape((-1, num_qubits))
ValueError: cannot reshape array of size 0 into shape (0)

this PR

SparsePauliOp(['III'],
              coeffs=[1.+0.j])

Although Pauli.apply_layout works correctly, I added the zero-qubit test cases to ensure it.

Details and comments

[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 9081444739

Warning: This coverage report may be inaccurate.

This pull request's base commit is no longer the HEAD commit of its target branch. This means it includes changes from outside the original pull request, including, potentially, unrelated coverage changes.

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Details

• 2 of 2 (100.0%) changed or added relevant lines in 1 file are covered.
• 21 unchanged lines in 2 files lost coverage.
• Overall coverage increased (+0.02%) to 89.651%

---

Files with Coverage Reduction	New Missed Lines	%
qiskit/dagcircuit/dagnode.py	8	88.12%
crates/circuit/src/circuit_instruction.rs	13	87.59%

Totals
Change from base Build 9037095581:	0.02%
Covered Lines:	62323
Relevant Lines:	69517

---

💛 - Coveralls

[t-imamichi]

I noticed that I have to fix Pauli as well.

[t-imamichi]

I confirmed that the current Pauli.apply_laytout works correctly. So, we don't have to update it. I just added tests to ensure it.

[ewinston]

Looks good although maybe could be made briefer using @data like test_zero_qubit_pauli_construction above.

[t-imamichi]

Thank you for your suggestion, Erick. I simplified this PR with combine.
I also applied isort to remove pylint: disable=wrong-import-order