Enhance configuration settings with command line arguments

[Mearman]

• Imported argparse in config.py to handle command line arguments.
• Added new configuration options to be handled by argparse.
• Configuration variables are now first attempted to be fetched from command line arguments, if not provided then environment variables are used, and if none is provided then defaults are used.
• Moved argument parsing from privateGPT.py to config.py.
• Removed parse_arguments function in privateGPT.py, as argument parsing is now handled in config.py.
• Configuration variables (including flags for hiding source and muting stream) are now fetched directly from the config module in privateGPT.py.