GitLab

Instead of using `out=pystr:<my.py>` we can now do this:
```
dynemo-run out=pytok:/home/graham/my_python_engine.py --model-path <hf-repo-checkout>
```

That engine will receive and respond with tokens. Here's an example engine file:
```
import asyncio

async def generate(request):
    yield {"token_ids":[791]}
    await asyncio.sleep(0.1)
    yield {"token_ids":[6864]}
    await asyncio.sleep(0.1)
    yield {"token_ids":[315]}
    await asyncio.sleep(0.1)
    yield {"token_ids":[9822]}
    await asyncio.sleep(0.1)
    yield {"token_ids":[374]}
    await asyncio.sleep(0.1)
    yield {"token_ids":[12366]}
    await asyncio.sleep(0.1)
    yield {"token_ids":[13]}
```

Also reduce duplication by making the bindings engine use the llm lib engine.