no function logs by default

[rdallman]

since we've accomplished #1055 now and the logs API is gone, there is no default logging story for functions for users that run fn start. this is kinda bad.

there are 2 ways to get logs now, neither of which are defaulted to:

• add a syslog url to an app
• set FN_LOG_LEVEL=debug / fn start --log-level=debug

one solution is that we could provide additional configuration to turn off the logs and allow setting the container log level, possibly defaulting to out of the box using 'info' level, but allow disabling this / setting to debug level. then users could see the logs from the fn start docker container or from their terminal in attached mode. these are not great, but a definite improvement over nothing. and having them available via docker logs allows running easy grep commands against call ids, etc.

fn start itself is a dind container, so we could do "interesting" things like leaving logs laying around in there somewhere. other ideas are welcome here.

[ruti1012]

I'm really looking forward to better local logging for development, as setting up a syslog server just for local development seems a bit too complicated. Acessing the logs via docker logs would be super nice!