Allow ignoring attribute read problems in read-resource calls

Occasionally we get reports like JBEAP-14637 where reads of large chunks of data are failing because of a problem with a single attribute. This RFE is about finding a way to make this more resilient if appropriate.

I chose Feature Request because I believe this will need to involve user configuration, i.e. we can't just ignore failures by default, with no user control. If we could it would be an Enhancement.

A PR like https://github.com/wildfly/wildfly/pull/11116 fixes this in a custom way by ignoring the failure (other than logging in server.log) and just issuing a management API WARN. But it would be better to have some sort of control, plus a central implementation. For example the WARN might be fine for a big recursive read-resource call, but it doesn't make much sense for a read-attribute call. And it might not make sense for many read-resource calls either. But HAL trying to read the entire /deployment=foo tree might want to configure ignoring failures.

So I was vaguely thinking about some param to read-resource to control this. And then figuring out how to ignore the failure and WARN in a generic way.