Add Watsonx embedding model

Comment From: PabloSanchi

I updated the embedding model following the new core interface requirements.

Comment From: PabloSanchi

@tzolov is it possible to merge it? it would make me a giant favour as I will be needing it for a project :) Thanks

Comment From: markpollack

will get to it soon.

Comment From: markpollack

Thanks again! Merged in 035036c7f20bbfcd85312c06e7dd0fbed56d4f71