Deprecate AiVdbProviderInterface::getVdbIds()

I think it depends on provider, in this case I think the problem was Milvus if I remember right (would have to check). Pinecone was fine for it. I suppose that could be a problem for Milvus specifically to sort then... Haven't checked others

Checked and this is doable, steps would be this I believe:

1. Copy the current state of deleteItems() from AiVdbProviderClientBase into Milvus
2. Remove the deleteItems() method from AiVdbProviderClientBase since its Milvus specific code that others currently override
3. Remove getVdbIds() from AiVdbProviderInterface
4. Do coordinated release (e.g. 2.0 branch) for Milvus

Given its experimental I don't think we need to do an actual deprecation throw unless others disagree. We can just add to release notes. Currently AI module homepage does not list any supported VDB provider other than Milvus that would need coordinated update.

Hmm actually we may need this for 📌 Improve AI Search Module Indexing to Handle Long-Running Chunk Embedding Processes Needs work for the ChunkQueueWorker. Going to postpone to see where that goes