Fix: log msui startup path and configured logfile location

[levi178u]

Purpose of PR?:

Fixes #2686

Changes done:

• logged the actual path of the script used to start MSUI using os.path.abspath(sys.argv[0]).
• Logged the current working directory using os.getcwd().
• Logged the configured log file path using args.logfile instead of hardcoding $HOME/.config/msui/msui.log