I would like to create the logfile inside uftrace.data directory by default so that external users can send it us simply with a single directory. And the name doesn't have to be different all the time.

The current implementation requires explicitly remove the previous logfile because its open mode is append, but we don't have to remove it anymore if it's created inside uftrace.data.
The previous discussion is in #707.

In addition, I think we don't have to provide logfile name explicitly. Why don't we just fix the logfile name as uftrace.data/logfile.txt? It will look a lot simpler.