.Net: Add vectorless search to record collection interface.

[westey-m]

Motivation and Context

Many of the databases that implement the vector store abstractions support search without vectors.
It is possible to search the database with a zero value vector anyway, but doing vector comparisons
without needing to is inefficient.

Description

• Adding a vectorless search method to the collection interface with implementations.

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 😄