Refactor secret and passportData management

[0xturboblitz]

Secret and passport data management is currently messy. There are many functions that have small variants, often have to handle JSON parsing and null/false returns.

Because this is so sensitive, right now we're trying never to change those functions to avoid breaking anything, but at one point we should refactor all of that on a branch and QA all the flows before merging.

Two useful facts:

• Except in the backup/recovery flow, we always need both secret and passport data at the same time. It is thus simplest to have functions that return both.
• We do not want to always require biometric authentication to access them, as they are often required for navigation. For instance, to know if the user is registered and if their passport is nullified onchain.