Functional implementation of the llm example

[Alanxtl]

I'm lixuetao. All of the features mentioned in #800 have implemented, which includes:

1. cli client: multi-turn conversations, command interact, context management.
2. web client: multi-turn conversations, binary file transform through rpc and support for LLM interactions

[AlexStocks]

Is this PR in progress or completed?

[Alanxtl]

Is this PR in progress or completed?

It is completed.

[Alanxtl]

@AlexStocks
Thanks for the careful comment, I've fixed all of the problems you mentioned, specifically:

1. Use imports-formatter to format all of the files.
2. Rewrite all of the Chinese comments.
3. Wrapping some of the functionality from chat.go to context.go, to reduce lock scope and achieve decoupling effect.

btw, there are three files
llm/go-client/frontend/templates/index.html
llm/go-client/frontend/static/script.js
llm/go-client/frontend/static/style.css
which I cloned from another repo and changed a lot of lines. However, this repo doesn't specify the open source license. I didn't add the ASF license to these files, and I added comments at the beginning of each file giving their source. I'm not sure if this is the right way or not.