[WFLY-15480] Refactor resource closing (appclient)

[boris-unckel]

Fixes https://issues.redhat.com/browse/WFLY-15480
as part of https://issues.redhat.com/browse/WFLY-15479

[bstansberry]

Hi @boris-unckel

Thanks for this but I have concerns about this overall project, here and in WildFly Core. I think we need to separate actual bugs from efforts at code reuse and very much limit the latter, as it in turn brings risks of bugs.

Any place where there is a new dependency being added in order to allow code reuse, that's questionable. If the dependency is coming from a different codebase that's unlikely to be acceptable. XNIO for example is not a utility library.

[boris-unckel]

@bstansberry thanks for your feedback. If I understand it correctly, XNIO (even as existing transitive dependency) must not be used for this purpose. A different utility like VFSUtils or the StreamUtils, even as existing dependency and in use, would not help because the refactoring is too risky.
In short this means I shall withdraw the series, correct?

[boris-unckel]

The proposed change series contains XNIO as dependency not wanted for this utility purpose and the overall value/risk ratio is too low. See PR14791 It's therefore withdrawn.