Optionalize mkTarget's 'humanName' and 'name' arguments by inferring
'humanName' from the 'name' attribute in the /modules/<MODULE>/meta.nix
file, and 'name' from the /modules/<NAME>/ directory name.
Inferring the 'humanName' and 'name' arguments ensures consistency and
reduces boilerplate.
The 'humanName' and 'name' arguments are optionalized instead of removed
because complex modules generating target derivations need to
distinguish between them.
Closes: https://github.com/nix-community/stylix/issues/1661
Rename mkTarget's 'configElements' argument to 'config' and
'extraOptions' to 'options' to provide a more transparent interface with
the underlying Nixpkgs module system.
