sqlite: expose backup api

[geeksilva97]

Closes #55413

This PR exposes the SQLite Online Backup API, which allows database backup.

The API is inspired by better-sqlite3 https://github.com/WiseLibs/better-sqlite3/blob/master/docs/api.md#backupdestination-options---promise.

Multithreading caveats

As long as writes come from the same process and handle (sqlite*), the backup will continue progressing as expected. Other than that, it can cause the backup process to restart. From docs:

...If the source database is not an in-memory database, and the write is performed from within the same process as the backup operation and uses the same database handle (pDb), then the destination database (the one opened using connection pFile) is automatically updated along with the source.

Writes to an in-memory source database, or writes to a file-based source database by an external process or thread using a database connection other than pDb are significantly more expensive than writes made to a file-based source database using pDb (as the entire backup operation must be restarted...)