Add logging for starting/finishing fuzzing for specific function

[tyuldashev]

Description

Currently from idea.log it's not possible to understand on which method UTBot Python works at the moment, so when I see some errors there I cannot link it to specific function under test which is problematic.

Expected behavior

Could we add a log entry for beginning [and ending] of test generation for each function, so the log would look something like:

Fuzzing started for function: use_dic(my_dict) -> int
....
Fuzzing finished for function: use_dic(my_dict) -> int

Exact method name in the log could be different of course, but better if it would be closer to what's written by user, so it would be easier to find.

Potential alternatives

We also could add function name to each log entry, when it's relevant. But this seems less pretty, as we don't always need that information every time we look in the log.

Context
When trying to investigate root cause of some issues, like #1830 it's needed to understand which error in the log belong to which function and which are not related.