Address basis interface changes in QuantumInterface

See https://github.com/qojulia/QuantumInterface.jl/issues/33 and https://github.com/qojulia/QuantumInterface.jl/pull/32 for details. Currently, the types `GaussianState`, `GaussianUnitary`, and `GaussianChannel` subtype `StateVector` and `AbstractOperator` from QuantumInterface. The parameterizations of these abstract types will be changed soon in QuantumInterface.