discovery: remove Singleton metaclass, update descendants name
discovery: remove Singleton metaclass, update descendants name

RedHat-Eng-PGM/python-schedules-tools,RedHat-Eng-PGM/schedules-tools,RedHat-Eng-PGM/schedules-tools,RedHat-Eng-PGM/python-schedules-tools,RedHat-Eng-PGM/schedules-tools,RedHat-Eng-PGM/python-schedules-tools