Harmonize our message protection logic with BouncyCastle's built-in logic

[ralienpp]

Consider whether we can use logic from BouncyCastle, or if BC can be adapted to follow our approach.

• Start with src/main/java/com/siemens/pki/cmpracomponent/protection and src/main/java/com/siemens/pki/cmpracomponent/msgvalidation/ProtectionValidator.java, bc-java/pkix/src/main/java/org/bouncycastle/cert/cmp/ProtectedPKIMessage.java
• Understand the difference
• Figure out how to best harmonize