.Net: Improve langchain interop sample further

[westey-m]

Motivation and Context

The sample could be improved by having a common data model that matches the one used in Lanchain, which also makes interoperable consumption of the different collections easier.

#9013

Description

• Added Pinecone to samples
• Added factories that expose the same data type for all vector stores
• Added key mapping for Qdrant so that it can use the same data model

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 😄