Security hardening (2.2 Caliptra core ROM): Key Clearing & Handoff between ROM -> FMC -> RT

[bharatpillilli]

(Since this will have ROM impact to configure FMC, RT regions, also duplicating the issue; ROM reps are aware of this as Vishal wanted to have some configurability but these registers themselves are shadow protected against attacks)

• On ROM to FMC transition, ensure no root keys are left in KV that FMC can use
• On FMC -> RT transition, ensure no root keys are left in KV that RT can use

This is to protect against ROM glitch attacks.

One of many enhancements that will happen as a part of this RFC: chipsalliance/Caliptra#652