This allows us to separate the initialization code from translations and error reporting.

This change changes the caller semantics of LoadChainstate quitendrastically.

To see that this change doesn't change behaviour, observe that:

1. Prior to this change, LoadChainstate returned false only in the "bad genesis block" failure case (by returning InitError()), indicating that the caller should immediately bail. After this change, the corresponding ERROR_BAD_GENESIS_BLOCK handler in src/init.cpp maintains behavioue by also bailing immediately.

2. The failed_* temporary booleans were only used to break out of the outer do/while(false) loop. They can therefore be safely removed.

ninja all check-extended