Enable backup creation and restoration from Rust

Summary: This differential provides boilerplate code so that we can call BackupOperationsExecutor from Rust.

Test Plan:

1. Comment line in DatabaseManager where we remove backup directory on log-out.
2. Add call to create_main_compaction in restore_backup in backup.rs
3. Add some logging to get encryption key.
4. Create some drafts.
5. Tap text backup restore protocol button.
6. Log out.
7. Replace call to create_main_compaction in restore_backup in backup.rs with a call to get_backup_file_path with previous backup id and restore_from_main_compaction with previous backup id and encryption key logged before log-out.
8. Tap text backup restore protocol button.
9. Restart the app. Ensure that drafts created before log-out are now present.

Reviewers: kamil, michal

Reviewed By: michal

Subscribers: ashoat, tomek

Differential Revision: https://phab.comm.dev/D10512