[native_rust_library] implement method to retrieve latest backup info

Summary:
ENG-6145.

This method will be used to get both backupID and userID.
There is some code duplication but later in the stack other function like retrieve_latest_siwe_backup_data or download_latest_backup_id are deprecated in favour of download_latest_backup_info (I had to somehow split this into diffs to make it easier for a review).
This function will be the main interface to get the backup latest info for both password and wallet users.

Depend on D13836

Test Plan: Tested in D13839

Reviewers: varun, bartek

Reviewed By: bartek

Subscribers: ashoat, tomek

Differential Revision: https://phab.comm.dev/D13837