Updates

[chaoming0625]

This pull request includes several changes aimed at enhancing functionality and improving code quality. The key changes include modifications to the ProgressBar handling, updates to XLACustomOp, and the addition of new classes and methods to support Poisson input functionality.

Enhancements to ProgressBar handling:

• brainstate/compile/_loop_collect_return.py: Updated the pbar parameter to accept either a ProgressBar instance or an integer, and added type checks and initialization logic accordingly. [1] [2] [3] [4] [5] [6]
• brainstate/compile/_progress_bar.py: Added an assertion to ensure that the freq parameter is greater than 0 when it is an integer.

Updates to XLACustomOp:

• brainstate/event/_fixedprob_mv.py, brainstate/event/_linear_mv.py, brainstate/event/_xla_custom_op.py: Renamed cpu_kernel_generator and gpu_kernel_generator to cpu_kernel_or_generator and gpu_kernel_or_generator for clarity and consistency. [1] [2] [3] [4] [5] [6]

Addition of Poisson input functionality:

• brainstate/nn/_dyn_impl/_inputs.py: Introduced the PoissonInput class and poisson_input function to generate Poisson input for a given brainstate.State. [1] [2]

Other notable changes:

• brainstate/event/__init__.py: Refactored imports and updated the __all__ list for better module organization.
• brainstate/event/_csr_test.py: Added a new test file with unit tests for the CSR class.
• brainstate/graph/_graph_node.py: Introduced graph_invisible_attrs to manage node attributes that should be ignored during graph operations. [1] [2]
• brainstate/nn/_dynamics/_dynamics_base.py: Added graph_invisible_attrs and new methods get_item_value and get_item to the Dynamics class. [1] [2]