QuTiP: GPU-enabled circuit simulation in qutip-qip

The current gate-level circuit simulator in qutip-qip utilizes a full sparse Qobj representation of each gate, expanding local gates to the Hilbert space before applying them to the state vector via matrix multiplication. This approach encounters significant memory and computational bottlenecks as the number of qubits increases. This project aims to address that limitation by refactoring the circuit simulator and adding tensor based executing via the recently added qutip.einsum. PR #225 in qutip-qip has made efforts to introduce a foundational tensor contraction approach, but it is only limited to the numpy backend and lacks support for GPU acceleration. Hence, this project aims to further implement JAX integration to the backend using qutip.einsum with JIT compilation for speedups on both CPU and GPU, As well as,to implement GPU accelerated circuit simulation using qutip-cuquantum.