Rework FBE crypto to match the N way of doing things

Major rework and refactor of FBE code to load the keys at the right
time and in a natural way. The old code was aimed at our goals for M,
with patches on top, and didn't quite work.

Bug: 22358539

Change-Id: I9bf7a0a86ee3f2abf0edbd5966f93efac2474c2c
4 files changed