Implement JNI interface to use C++ code to update thread unread status on Android
Summary: Implement JNI files to expose C++ thread update functionality to CommNotificationsHandler.java
Test Plan: No testing plan. Child differential will use those files to update thread unread status in CommNotificationsHandler and will provide testing plan.
Reviewers: palys-swm, atul, varun
Reviewed By: palys-swm
Subscribers: ashoat, Adrian, yayabosh
Differential Revision: https://phab.comm.dev/D4236