Logging fixes

[agateau-gg]

This small PR make a bunch of small logging fixes, mainly for secret scan ci but not only:

• Information reported when called with --verbose is now also logged, so using --debug without using --verbose does not end up with less information.
• When called with --debug, secret scan ci now also logs the list of commits to scan.
• Fix a case where we were using the root logger instead of the logger defined in the module

[Paul-GitGuardian]

Nice!
Maybe log_vars should be moved to an higher level? I think it could be used in previous_commit.py too

[agateau-gg]

Nice! Maybe log_vars should be moved to an higher level? I think it could be used in previous_commit.py too

Good idea, going to do this.