Resolve config files with less spaghet

[TheToddLuci0]

While hunting another issue, the spaghetti that is options resolution was getting rather annoying. So I replaced it with something much less tasty, but also much cleaner.

Basically, it uses the ArgumentParser.set_defaults method to update the defaults with the config files at runtime. This manes that we get the same behavior of "CLI wins", while also reducing the need to manually update a self.foobar = args.foobar or config_dict.get("foobar") every time a change is made to the args.

The downside is that it calls parser.parse_known_args() twice, but the actual runtime difference is, as far as I can measure, zero. Might matter if anyone is running credmaster on a 3DS.

[TheToddLuci0]

A quick PoC to show the precedence order still works. (note that a debug print was added just before instantiating the CredMaster object)

(venv) ┌──(venv)─(kali㉿kali)-[~/git/CredMaster]
└─$ tail credmaster.py -n 3                                                          
        # Debug print for demo
        print(f"Current profile: {args.profile_name}")
        CredMaster(args, pluginargs)
                                                                                                                                                                                    
(venv) ┌──(venv)─(kali㉿kali)-[~/git/CredMaster]
└─$ python3 credmaster.py --plugin template 2>/dev/null | grep "Current profile" 
Current profile: None
                                                                                                                                                                                    
(venv) ┌──(venv)─(kali㉿kali)-[~/git/CredMaster]
└─$ python3 credmaster.py --plugin template --config aws.config 2>/dev/null | grep "Current profile"
Current profile: credmaster
                                                                                                                                                                                    
(venv) ┌──(venv)─(kali㉿kali)-[~/git/CredMaster]
└─$ python3 credmaster.py --plugin template --config aws.config --profile testey_mc_testerson 2>/dev/null | grep "Current profile"
Current profile: testey_mc_testerson

The 2>/dev/null is due to #90