Weld 5 - decide on how to include support for build compatible extensions

Next CDI version includes build compatible extensions (currently part of Alpha release of CDI API) and Weld will have to support them somehow.

Easiest way to execute these extensions is via one Portable Extension as Ladislav did here - https://github.com/Ladicek/StillDI (the impl directory).

IMO Weld should basically just take this impl and include it in one way or another. It can be a separate module, part of core or any other way. However, it will probably have to be part of all Weld variations by default.