Make handlers to decouple with ignite APIs

Is your feature request related to a problem? Please describe.
According to our design principle, almost all the MONAI components can be easily integrated into other workflows or PyTorch programs except for handlers.
As handlers contain many important features, users who are using other workflows also want to integrate them.
After analysis with ignite team: https://github.com/pytorch/ignite/issues/2000, actually it's possible to extract ignite related logic from handlers as utils and make most of the handlers to be independent from ignite, except for some handlers that are based on ignite handlers or ignite distributed data parallel.
So I plan to implement based on the discussion and start from inference related handlers.