[WFLY-543] : Provide an operation to request service status report after server has been started

Adding the new command "read-boot-errors" available from core-service=management to list all operations that failed during boot.
It displays all boot errors with the failed operation and the failure description / exception of the error.
Jira: https://issues.jboss.org/browse/WFLY-543
It's not just a List<String>; it's structured data. Tomaz, we're not going to give up providing structured data. But, we have to be able to describe the reply exactly.

Unfortunately, it looks like we need to improve SimpleOperationDefinitionBuilder and DefaultOperationDescriptionProvider to make that possible.