Provides request object into exception handler

This PR allows loggers such as Sentry get access to a request object constructed by the DRF using custom exception handler.

Problem was fully described here: #1380 

I've also made this change BC, so if one has custom exception handler which does not expect additional parameter to be passed - nothing bad will happen.

P.S. Probably this BC needs some removal schedule comment which is up to maintainers of course.