feat: Qdrant external retriever

[Anush008]

Description

This PR adds support for external retrieval using Qdrant - https://qdrant.tech. Includes docs and examples.

Unit and E2E tests using a local Qdrant instance have been set up.

Type of Change

• [x] New feature
• [x] Documentation update

Note

I have agreed to and signed the CLA(cla@neo4j.com).