refactor: Restore QdrantRM

[Anush008]

Description

This PR restores the QdrantRM retriever, which was previously commented out in #1937 due to its reliance on deprecated dsp/* module imports.

To resolve this, all necessary imports have been made inline. This change restores QdrantRM's original functionality.

[okhat]

Thank you @Anush008 ! Q: Do you think this code should live inside DSPy? It seems like it can just be an external piece of code.

[Anush008]

We've had several users of QdrantRM over time. So I propose to keep it. The dependencies are optional.

[okhat]

We love Qdrant, but this could be a new pip library maybe? pip install dspy-qdrant? It doesn't seem like this should live inside DSPy; it'll get stale etc.

[Anush008]

I believe a library would be an overkill.
Since there are several retriever implementations in https://github.com/stanfordnlp/dspy/tree/main/dspy/retrieve already, this would be another addition(restoration).

[okhat]

Oh all of these are getting deleted, see then recent PR: #8073

[Anush008]

Oh. Makes sense then. Thanks.

[Anush008]

Hey @okhat.
We'll move the retriever to a separate qdrant-dspy package.

[Anush008]

https://github.com/qdrant/dspy-qdrant