chore(ci): log with info to stdout and debug to log file

Currently, renovate-runner logs to stdout with debug, but gitlab truncates job logs in the UI if they are larger than 500KB, so the user would need to download/view the raw job log in any case. I get a job log of >1MB with about 80-90 repos with a dry run already.

I think it's more sensible to only provide a concise job log with info and if the user needs to investigate further a log file is provided as a job artifact.