remove owned_session

[grimoire]

session is no longer bind to EngineInstance.

Tested on chat and profile_pytorch_benchmark with llama-7b

[AllentDan]

I've tested OK for both pytorch and turbomind concurrency. But there is a VRAM increase during benchmarking restful API for pytorch backend.

[AllentDan]

Besides, the performance gap between benchmark/profile_torch_throughput.py and benchmark/profile_restful_api.py is far larger than turbomind backend.

[AllentDan]

I found for api_server, if I make requests on 64 concurrency, the actual concurrency for the pytorch backend is only 10+. Do you have any clue about it?

[grimoire]

queue get will block cpu on coroutine. I have update an version with async recv. in 6b6dcae

But since all tokenizer are processed on the same cpu with the engine, it still can not reach the performance of profile throughput.

[AllentDan]

LGTM