rename/alias `PauliLindbladMap.get_qubit_sparse_pauli_list_copy` as `PauliLindbladMap.generators`

[aeddins-ibm]

One thing the classes PauliLindbladError (Runtime) and PauliLindbladError (Aer) agree on is providing their error generators via the attribute generators.

It would be helpful if PauliLindbladMap (Quantum-Info) also exposed generators as either an attribute or method. Maybe a simple solution is to rename (or alias) the existing method PauliLindbladMap.get_qubit_sparse_pauli_list_copy, which seems too verbose.

[DanPuzzuoli]

I think I think the move here is to not rename but to just add a .generators method that calls get_qubit_sparse_pauli_list_copy. In #14901 we are looking at unifying/abstracting some of the code for these rust-backed classes that contain a qubit sparse pauli list. It's been a while since I've thought about it but get_qubit_sparse_pauli_list_copy is likely to be a method that we will want in this abstraction.

I'd be happy to add the generators method in a small PR if that would be useful.