Inline unchanging Msf::Config::Defaults

MSP-9228

Only 'ConfigDirectory' is written in metasploit-framework, so remove all
other defaults and just inline their hard-coded value.
Remove Msf::Config methods that don't depend on config directory

MSP-9228

Change it to use Metasploit::Framework.pathnames and its methods as the
changed paths are all dependent on Metasploit::Framework.root and not
changeable by changing the config directory.