.Net: [MEVD] Added GetService and Metadata for vector store abstractions

[dmytrostruk]

Motivation and Context

Related: #11013

This PR marks IVectorStoreRecordCollection.CollectionName property as obsolete in favor of Metadata classes and GetService method (the approach which is also used in MEAI).

GetService method is added to each vector store interface and each implementation is updated to return Metadata classes or underlying services used for breaking-glass scenarios. (Note: this is a breaking change for already existing implementations, since new GetService method should be implemented).

The changes allow to:

• Extend vector store related metadata by exposing not only CollectionName, but other properties like VectorStoreName, DatabaseName and any other potential properties in the future. These properties are going to be used in telemetry decorators, which will be implemented in separate PR.
• Get access to underlying services used by vector store implementations for breaking-glass scenarios (when functionality from abstraction is not enough to handle a specific use case).

@westey-m @roji

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 😄

[roji]

LGTM after comments are addressed, thanks @dmytrostruk!

[roji]

@dmytrostruk I think we're missing extensions over the new GetService(), as in MEAI. This can be added later without breaking, but I do want to at least make sure you have it tracked somewhere? It's also pretty trivial in case you just want to submit a PR and fix it.

[roji]

This fails for e.g. Weaviate, where there's no VectorStoreName (I guess we're not running these integration tests in CI?).