LibNativeBridge: Version 2

Add a callback function to retrieve "signal handler" from the bridge,
if the bridge wants it to be managed by the runtime. The signal handler
will be invoked after the runtime's own one, and before any other
chained handler.

Add a callback function to check compatibility of the bridge with the
library.

Add a function to expose the native bridge version. Add a test for this
function.

Bug: 20217701

(cherry picked from commit a6ac9ce9)

Change-Id: Ic23a60b949f119c7d8b0e7cb27a61e6c16532a23