Change Details

[ENG-10126](https://linear.app/comm/issue/ENG-10126/restore-the-old-userdata-key-during-user-keys-restoration). Alternative is to do it at the end of `getBackupUserKeys` call, however I decided to do it like it because of two reasons: 1. `getBackupUserKeys` is a promise resolved by Rust, we'll need to implement Rust calling `setUserDataKeys` and scheduling on Database thread which is more complex. 2. We might want to call `getBackupUserKeys` just to inspect to return value without setting key and rekeying database, it is better to do it only when needed, directly from restore protcol. Depends on D14268

[ENG-10126](https://linear.app/comm/issue/ENG-10126/restore-the-old-userdata-key-during-user-keys-restoration). The alternative is to do it at the end of the `getBackupUserKeys` call, however, I decided to do it like it because of two reasons: 1. `getBackupUserKeys` is a promise resolved by Rust, we'll need to implement Rust calling `setUserDataKeys` and scheduling on the Database thread which is more complex. 2. We might want to call `getBackupUserKeys` just to inspect to return value without setting the key and rekeying the database, it is better to do it only when needed, directly from the restore protocol. Depends on D14268

[ENG-10126](https://linear.app/comm/issue/ENG-10126/restore-the-old-userdata-key-during-user-keys-restoration). AThe alternative is to do it at the end of the `getBackupUserKeys` call, however, however I decided to do it like it because of two reasons: 1. `getBackupUserKeys` is a promise resolved by Rust, we'll need to implement Rust calling `setUserDataKeys` and scheduling on the Database thread which is more complex. 2. We might want to call `getBackupUserKeys` just to inspect to return value without setting the key and rekeying the database, it is better to do it only when needed, directly from the restore protcolocol. Depends on D14268