Refactor parts of FalsingManager into FalsingCollector

This CL separates out the two roles of the FalsingManager. It
introduces the FalsingCollector, used by SystemUI to report events
that may be interesting to Falsing, such as touch events, sensor
events, and general user actions.

The FalsingManager, meanwhile, continues to support the methods

This helps breakup the monolithic FalsingManger into more manageable
pieces, reducing the API surface area of FalsingManager significantly.

Bug: 172655679
Test: atest SystemUITests && manual
Change-Id: I92f8e3747f5c4a04eaa64e1a8b626c2a07c480aa