Wires: add missing requires
turn Wires.from_hash into .from_array
add Wires#+
Circuit#wire_to: use Wires#+
Circuit#{is,os,ps,qs}_wires: use Wires.from_array
Circuit spec: add a missing require
fix Circuit#== spec
add Circuit#add_wires
FunctionDecomposer::Parallel: use Circuit#add_wires
FunctionDecomposer::Parallel: use Wires.from_array
factor out FunctionDecomposer::Parallel::Wirer