Introduce InputConfig::SENSITIVE_FOR_TRACING

We don't want to rely on WM flags in input, and we also want to be able
to mark a window as secure in the input framework without affecting
other aspects of the system.

Introduce a new InputConfig flag for sensitive windows. It must always be
set when the window flag FLAG_SECURE is set.

Bug: 210460522
Test: manual
Change-Id: I5adb7467ab76bdcf89803e1ba08b52273a09e7bb