Discussion of MP compatibility guarantees in WildFly docs

The MP specifications innovate more rapidly than EE historically has and the MP community is more willing to accept incompatible changes than EE historically has been. The result is the MP features the WF provides may change in incompatible ways between releases more frequently than typical WF features do. We should have some discussion of this in our documentation.

• The Admin Guide sections on the various MP subsystems should have some mention of this fact, focused on how output formats may change (if relevant for a spec) or how management API may change if a spec change forces an integration change that in turn requires an incompatible management API change (not expected but possible.)
• The Developer Guide should have a brief Microprofile section that highlights this fact, but focused on user API and output formats. There can be subsections for the specs we support (where we have useful content) that can provide brief further details; e.g. links to things like the MP Metrics spec changelog.