Make toasts non-clickable

Since enforcement was only on client-side, in Toast class, an app could
use reflection (or other means) to make the Toast clickable. This is a
security vulnerability since it allows tapjacking, that is, intercept touch
events and do stuff like steal PINs and passwords.

This CL brings the enforcement to the system by applying flag
FLAG_NOT_TOUCHABLE.

Test: Working on CTS test
Test: Construct app that uses reflection to remove flag FLAG_NOT_TOUCHABLE and
      log click events. Then:
      1) Observe click events are logged without this CL.
      2) Observer click events are not logged with this CL.
Bug: 128674520

Change-Id: Ic36585bc4f186e0224f5b687c49c0b3d9266838c