[issue172] Migrate to a Jakarta namespaced activation API.

[jamezp]

Upstream is #176, however this one is a bit different. #152 seemed to partially solve this, but never changed the package names. I noticed it imports the implementation too instead of the API, which might be required but I'm not sure. The 2.13 won't currently compile without this change.

Let me know if the API vs the implementation is preferred and I can either change this PR or the upstream #176 one.

[cowtowncoder]

I think API should be preferred, not implementation, assuming that's where JAXB/Jakarta-XML-bind annotations live: module makes no use of actual implementation. Unless unit tests used it? (if so, impl should be test-only dependency).

However... I wonder if there are issues wrt backwards compatibility within minor version, wrt impl vs api.
But the main reason I suspect it's fine is that "Jakarta" variants were only added in 2.13 (as per https://github.com/FasterXML/jackson/wiki/Jackson-Release-2.13) so there isn't much usage; and it is likely that anyone trying to use the module might have hit this same issue.

So I will rely on your expertise @jamezp here: I assume your assessment is correct.

[jamezp]

Okay perfect. I think the API is appropriate here as well. I've updated this PR to use the API and I'll close the 2.14 one. Thank you!

[jamezp]

resolves #175