Implement Android Verified Boot app components

This patch implements the major components for the AVB secure app.
The AVB secure app currently only handles rollback counters.

avb_messages   - describes format of AVB request/response messages
avb_manager    - implements callbacks invoked when the app receives a
                 request.
secure_storage_interface
               - abstract storage interface
secure_storage - implementation of SecureStorageInterface that uses
                 Trusty storage lib

Bug: 33051168
Change-Id: Idc169cc1b027bba12aae8915056d3810bd89c1e6
7 files changed