Make oneshot and keep-alive kernel handle error message more uniform

[cderv]

See context at #12238

• keep alive uses a server, and communicate with message, which allows main TS quarto code to catch errors, and log them using error()
• one shot kernel does only use stderr to write from Python side a Status no matter their type. This makes it hard to log as error() from TS side.

Moreover

• --log defines the main log file,
• But python has also its own logging writing to jupyter-kernel.log for debug.

Idea is to make the error logging more clearer in our code base and useful for debugging.