Dist::Zilla::Tester: Forcibly convert global_config_root to a Path::Class::Dir in _new_from_profile.

This also absoluteizes paths after coercion because it seems a very common requirement.

See : https://metacpan.org/source/ETHER/Dist-Zilla-PluginBundle-Author-ETHER-0.063/t/02-minter-github.t#L25

Fix: Make this absolute because it probably should be