Return touched windows from findTouchedWindowTargetsLocked

This is mostly a cosmetic change to modify the function to return things
that it promises to return in its name.

In the future, we will refactor this further to make it const and
possibly to remove goto.

Also, do a similar refactor for the focused events.

Bug: 211379801
Test: atest inputflinger_tests
Change-Id: Ib379628c59a6cc724e1c49e39068483c563ef56c