SectionRef::getName() returns std::error_code now.
Returning Expected<> instead has multiple benefirs
For example, it forces user to check the error returned.
Also Expected<> may keep a valuable string error message,
that is more useful than having a error code.
(Object\invalid.test was updated to show the new messages printed.)
This patch makes a change for all users to switch to Expected<> version.
Important note: in a few places the error returned was ignored before my changes.
In such places I left them ignored. My intention was to convert the interface
used, and not to improve and/or the existent users in this patch.
(Though I think this is good idea for a follow-ups to revisit such places
and either remove consumeError calls or comment each of them to clarify why
it is OK to have them).