Python binding for web-rwkv.

• Basic V5 inference support
• Support V4, V5 and V6
• Batched inference

1. Install python and rust.

2. Install maturin by

   $ pip install maturin

3. Build and install:

   $ maturin develop --release

4. Try using web-rwkv in python:

   import web_rwkv_py as wrp
   
   model = wrp.Model(
      "/path/to/model.st", # model path
      quant=0,             # int8 quantization layers
      quant_nf4=0,         # nf4 quantization layers
   )
   model.clear_state()
   logits = model.run([114, 514])

1. Get, clone and load current state:

   logits = model.run([114, 514])
   state = model.back_state(wrp.StateDevice.Gpu)
   # state = model.back_state(wrp.StateDevice.Cpu)
   state_cloned = state.deep_clone()
   
   model.load_state(state_cloned)
   logits = model.run([1919, 810])

2. Return predictions of all tokens (not only the last's):

   logits, state = model.run_full([114, 514, 1919, 810], state=None)
   assert(len(logits) == 4)