feat: Support `--main-gpu` in the ggml plugin

[hydai]

Summary

When using the ggml plugin in a multiple-GPU machine, it's important to specify the main GPU. The default value is using GPU 0 now.

Details

• Support --main-gpu, see https://github.com/ggerganov/llama.cpp/tree/master/examples/main#additional-options

Appendix

No response