[Tools] Add convert tools in xft.

[Duyi-Wang]

Usage：

import xfastertransformer as xft
converter = xft.LlamaConvert()
converter("/data/llama-2-7b-chat","/data/llama-2-7b-chat-xft", "fp16")

Params:input_dir, output_dir=None, dtype: str = "fp16", processes=8
if output_dir is None, default use input_dir with a suffix -xft, like:

converter("/data/llama-2-7b-chat")
# use output_dir = "/data/llama-2-7b-chat-xft"

Support converter list:

LlamaConvert
ChatGLMConvert
ChatGLM2Convert
OPTConvert
BaichuanConvert

TODO:

• README
• Lazy import
• hugging face dependency version

[changqi1]

python -c "import xfastertransformer as xft; xft.LlamaConvert().converter("/data/llama-2-7b-chat","/data/llama-2-7b-chat-xft", "fp16")"