.Net: Add qdrant vector search implementation.

[westey-m]

Motivation and Context

As part of the work on vector storage we have to add vector search capabilities for each implementation.

Description

1. Adding vector search for Qdrant.
2. Note that for now, the search interface is implemented directly by the collection, but in future it should be part of the collection interface. I'm doing it this way so that each implementation can be added one by one, and once all have been implemented, we can make the switch.

Contribution Checklist

• The code builds clean without any errors or warnings
• The PR follows the SK Contribution Guidelines and the pre-submission formatting script raises no violations
• All unit tests pass, and I have added new tests where possible
• I didn't break anyone 😄