Introduce INPUT_FEATURE_SENSITIVE_FOR_TRACING

This new input feature flag will allow a window to be treated as
sensitive for input tracing without explicitly needing the window to
also have FLAG_SECURE.

When the input feature is set, it will get converted to
InputConfig::SENSITVE_FOR_TRACING. Windows with FLAG_SECURE will
automatically have this InputConfig set in SF.

In particular, this will be used to mark the lockscreen as sensitive on
all builds so that it doesn't show up in input traces, even when
FLAG_SECURE is not set.

Bug: 210460522
Test: manual
Change-Id: Iabc38277749d561dd44ea2e3ac3471ca65316796