[v1.16.0] add into_vector interface for VectorOutput

[generall]

VectorOutput field contains deprecated vector representation of fields data, indices and vectors_count. We want to switch it to oneof vector field, which is more extendable and easier to work.

In order to do it nicely, we need to do it in several steps:

• Step 1 (current, 1.16.0): Provide universal interface to read vectors, independent from protocol-level vector representation, deprecate direct access to fields.
• Step 2: Switch server-side field from old to new (1.17.0)
• Step 3: Remove old fields (1.18.0)

[Anush008]

Should we mark deprecation of these fields too?

https://github.com/qdrant/qdrant/blob/20db14f87c861f3958ad50382cf0b69396e40c10/lib/api/src/grpc/proto/points.proto#L68C1-L71

[generall]

Should we also mark deprecation of these fields too?

I think yes, we already use builders for those, so the transition should be even easier

[generall]

It would depend on qdrant/qdrant#7185 unfortunately though