logger: Deprecate default logfile name

I believe API users, and not the library, should be responsible for
setting log file name.

include/libdnf5/logger/factory.hpp

@@ -28,8 +28,10 @@ along with libdnf.  If not, see <https://www.gnu.org/licenses/>.
 namespace libdnf5 {
 
 // File logger destination filename.
+/// @deprecated The filename should be set by API user.
 constexpr const char * FILE_LOGGER_FILENAME = "dnf5.log";
 
+/// @deprecated It is going to be removed.
 /// @brief Helper method for creating a file logger.
 /// @param base Reference to Base for loading the configured logger path.
 /// @return Instance of a new file logger.