Create device spec for the given qubits and coupled pairs.

qubits Qubits that can perform single-qubit gates.
pairs Pairs of coupled qubits that can perform two-qubit gates.
gate_sets Gate sets that define the translation between gate ids and cirq Gate objects.
durations_picos A map from gate ids to gate durations in picoseconds.
out If given, populate this proto, otherwise create a new proto.