[ANativeWindow] Add test infrastructure for apex apis

* Add ANativeWindow_getLastDequeueDuration as proof of concept
* Add ANativeWindowTest harness
* apex/ include directory for code living in apex modules, so that vndk
or system apis aren't pulled in
* TEST_MAPPING configuration for presubmit

Note that we're not piggybacking off of the existing Surface_test
harness, as those tests assume that the libgui Surface is The
ANativeWindow surface implementation, which means that those tests may
test implementation details that the harness defined in this change
should not attempt to test. Further, if an alternative implementation is
provided (e.g. an ANativeWindow -> BLAST adapter), we should be able to
parameterize the tests here. For now, however, we'll keep the assumption
that Surface is the only relevant surface implementation so that nonzero
tests may be written.

Bug: 137012161
Bug: 137012798
Test: libnativewindow_test
Change-Id: I0dddc348563ba95530fb1bd04bde66080755a91d