Support DepolarizingChannel for multiqubit gates

[ikkoham]

Required prerequisites

• Search the issue tracker to check if your feature has already been mentioned or rejected in other issues.

Describe the feature

DepolarizingChannel can be defined for multiple qubits.
For example, the following code should work as expected:

import cudaq
cudaq.set_target("density-matrix-cpu")

depolarization_channel = cudaq.DepolarizationChannel(probability=0.3)

noise_model = cudaq.NoiseModel()
noise_model.add_all_qubit_channel("cx", depolarization_channel)

@cudaq.kernel
def test():
    q = cudaq.qvector(2)
    x(q[0])
    cx(q[0], q[1])

print(cudaq.sample(test, noise_model=noise_model))