Log for light grey API accesses.

For the public Beta 1 build, it seems likely that 3P devs will want to
check the logcat for hidden API accesses by their own apps. So enable
this logging for light grey API accesses.

The option can easily be diabled again later by setting the new flag to
false (which should be done before public release).

Bug: 64382372
Test: m
Test: Verify logcat output
Change-Id: Ie610ebcf712a0abc3f1c200510048e2c93b712f7