Add 'status' command to get server status

[vowelparrot]

Example:

$ langchain plus start --expose
...
$ langchain plus status
The LangChainPlus server is currently running.

Service             Status         Published Ports
langchain-backend   Up 40 seconds  1984
langchain-db        Up 41 seconds  5433
langchain-frontend  Up 40 seconds  80
ngrok               Up 41 seconds  4040

To connect, set the following environment variables in your LangChain application:
LANGCHAIN_TRACING_V2=true
LANGCHAIN_ENDPOINT=https://5cef-70-23-89-158.ngrok.io

$ langchain plus stop
$ langchain plus status
The LangChainPlus server is not running.
$ langchain plus start
The LangChainPlus server is currently running.

Service             Status        Published Ports
langchain-backend   Up 5 seconds  1984
langchain-db        Up 6 seconds  5433
langchain-frontend  Up 5 seconds  80

To connect, set the following environment variables in your LangChain application:
LANGCHAIN_TRACING_V2=true
LANGCHAIN_ENDPOINT=http://localhost:1984