xPU Initial State picture with secure storages

[glimchb]

also see the main RFC8572:

5.1. Initial State
 +-------------------------------------------------------------+
 | <device> |
 | |
 | +---------------------------------------------------------+ |
 | | <read/write storage> | |
 | | | |
 | | 1. flag to enable SZTP bootstrapping set to "true" | |
 | +---------------------------------------------------------+ |
 | |
 | +---------------------------------------------------------+ |
 | | <read-only storage> | |
 | | | |
 | | 2. TLS client cert & related intermediate certificates | |
 | | 3. list of trusted well-known bootstrap servers | |
 | | 4. list of trust anchor certs for bootstrap servers | |
 | | 5. list of trust anchor certs for ownership vouchers | |
 | +---------------------------------------------------------+ |
 | |
 | +-----------------------------------------------------+ |
 | | <secure storage> | |
 | | | |
 | | 6. private key for TLS client certificate | |
 | | 7. private key for decrypting SZTP artifacts | |
 | +-----------------------------------------------------+ |
 | |
 +-------------------------------------------------------------+