Ontology widget - The widget blocking while recomputing scores

[PrimozGodec]

Followup of #832 and #882
The Ontology widget recomputes scores (when the ontology is changed). It calls embeddings in the main thread, which blocks the widget.

Expected behaviour

Computing the score should be called in a separate thread (i.e. with the concurrent mixin) that it does not block the Ontology widget.