Use DBIx::Class::Schema::Config for database config files

[preaction]

Right now we're using the configuration system built-in to DBD::mysql called mysql_read_default_file. The database information and credentials are stored in ~/.cpanstats.cnf and are put there by the cpantesters-deploy Rexfile. This works fine, but only for MySQL. Other databases need their own way of handling credentials, which many of them simply don't have, putting the onus on us.

The DBIx::Class::Schema::Config module provides this configuration feature for all database drivers. We should use this module and provide the appropriate configuration files in a read-only area of the machine. Edits will also need to be made to the the cpantesters-deploy Rexfile to deploy this new configuration file.

Once this is done, we can remove the connect_from_config method in the existing CPAN::Testers::Schema class.