Allow to do vector search by user supplied query

I don't think we should do this in AI module; we rely on the generation of the vector during search matching exactly the process used to generate the vectors during indexing.

Would be open to an Event developers can subscribe to allowing $params in SearchApiAiSearchBackend::search() to be modified (in which case they can (at own risk) provide $params['vector_input'] (since we check if that's empty first already before generating).

Hey @scott.
The code change I have pushed takes the vector input param from the query option.
So we can add it to the query during query alter phaese or while writing the vector services provider.

That makes sense! I'll try to get to manual testing this week.

Thank you!
I myself have not tested it thouroughly.
Will update if I face any issues because of this change.

Coding standards fails on the MR

Suggesting a slight refactor here as the code is getting a lot of nested ifs which makes it harder to follow + we have some inefficiency since we load embedding engine yet don't need to in your new case where we have an embedding already

Thanks!