[lib][native] Add keyserverDeviceID to LatestBackupInfo

Summary:
Propagate keyserverDeviceID from Rust backup client up to JS

Depends on D14467

Test Plan: console.log keyserverDeviceID when restoring user with keyserver present

Reviewers: kamil

Reviewed By: kamil

Subscribers: ashoat, tomek

Differential Revision: https://phab.comm.dev/D14489