glob is more flexible and simplifies the function arguments drastically.
It is also much more intuitive to extend in the future when the filepaths
need to be extended or changed.
setup_logger had to be called as the first thing after instantiation, so
this commit simplify makes it automatic.
Several clarification comments are added too.
Signed-off-by: Yuto Takano <yuto.takano@arm.com>