v4.0.0

Added

• Python 3.11 support.
• Purification of Gaussian states.
• PureFockState.get_tensor_representation for embeddng the state vector into
  a tensor with rank equal to the number of modes.
• Batch processing of pure Fock states.
• CVQNN module.
• Support for tf.function in PureFockSimulator.
• Supporting JAX in PureFockSimulator.

Fixed

• Error in custom gradient of passive linear gates in PureFockSimulator.

Breaking changes

• Python 3.7 support dropped.
• TensorflowPureFockSimulator has been deleted. Instead, one can use
  PureFockSimulator with TensorflowCalculator specified.
• Printing format of Fock states have been changed.
• Renamed _state_vector to state_vector.