Send mapper events via context

Currently, mappers report input events directly to InputListener
(InputClassifier, formerly InputDispatcher). To do this, mappers have to
pull a lot of information from context first, and then report it to the
listener.

If we move this call into context, then mappers don't even need to know
about the existence of Notify*Args.

This will also allow us to consolidate places where event id is
generated.

This, in turn, will help us report the input event statistics from a
more centralized place, where we already know event id, and also know
the read time of the event.

Bug: 169866723
Test: atest inputflinger_tests
Change-Id: I30e7b1418d006d3146ee02b775f524faa28b65ae