Provide guidance for OSGi integration

**Is your feature request related to a problem? Please describe.**
Different spec/impl projects currently use different approaches to integrate with OSGi frameworks

**Describe the solution you'd like**
Platform provides/defines consistent approach to integrate with OSGi for those who wants to opt-in supporting it, with minimal required OSGi runtime version eventually

**Describe alternatives you've considered**
Use org.glassfish.hk2.osgiresourcelocator, use the OSGi ServiceLoader mediator standard, follow http://docs.osgi.org/reference/portable-java-contracts.html#references

**Additional context**
https://github.com/eclipse-ee4j/saaj-api/issues/43#issue-482689004

[AB#76](https://dev.azure.com/jakarta-ee-azdo/7cf9a9d3-9854-41e0-9a66-99506a9ed874/_workitems/edit/76)

Start with the linked saaj-api issue #43 and compare the three approaches named here: org.glassfish.hk2.osgiresourcelocator, the OSGi ServiceLoader mediator standard, and the portable Java contracts reference. The issue is done when the platform has a documented, consistent opt-in integration approach and a defined minimum OSGi runtime version.

Written by the indexing model from the issue text.