Implement C++ file to expose backup API
Summary:
This differential implements C++ class that allows to safely trigger backup creation and restoration from any place in C++ using GlobalDBSingleton. The real
application ofthis class will be exposing C++ backup API to Rust in the very next diff.
Test Plan: The same as for the parent differential but instead of directly calling SQLiteQueryExecutor call methods of this class.
Reviewers: kamil, michal
Reviewed By: michal
Subscribers: ashoat, tomek
Differential Revision: https://phab.comm.dev/D10509