add support new backup format

[khimaros]

with the update to android 12, seedvault has also bumped the metadata version.

it would be great to be able to use this tool with newer backups.

[khimaros]

@chirayudesai says:

There's a doc in the storage section which this format shares some things with otherwise it should all be https://github.com/seedvault-app/seedvault/pull/327

@grote says:

mostly this with a different key id: https://github.com/seedvault-app/seedvault/blob/android12/storage/doc/design.md I think there's a python version of tink to make your life easier. The k/v backup is a zipped DB now, I think there's no docs on this.

here's the tink library: https://pypi.org/project/tink/

[khimaros]

https://github.com/seedvault-app/seedvault/issues/383 will be helpful for testing this change