Implement support for SQL Server VECTOR_DISTANCE()

[roji]

Note: this does not include VECTOR_SEARCH[] translation support (as opposed to VECTOR_DISTANCE() which is included); this is tracked by #36384.

Closes #34659

[Copilot]

Pull Request Overview

This PR implements SQL Server vector search support for Entity Framework Core, adding the ability to work with SQL Server's VECTOR data type and related functions. The implementation provides type mapping, query translation, and validation for vector operations.

Key changes include:

• Added SqlServerVectorTypeMapping for SQL Server's VECTOR type with proper dimensions support
• Implemented query translation for vector distance functions and vector properties
• Added model validation to ensure vector properties are properly configured and not used in unsupported scenarios

Reviewed Changes

Copilot reviewed 17 out of 18 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
SqlServerVectorTypeMapping.cs	New type mapping class for SQL Server vector type with custom comparer and literal generation
SqlServerVectorTranslator.cs	Query translator for vector functions (VectorDistance) and vector member access (Length)
SqlServerTypeMappingSource.cs	Updated to register vector type mapping and handle SqlVector<float> CLR type
SqlServerModelValidator.cs	Added validation for vector properties requiring dimensions and preventing use in JSON
SqlServerDbFunctionsExtensions.cs	Added VectorDistance function extension for calculating distances between vectors
SqlServerDatabaseModelFactory.cs	Updated scaffolding to properly handle vector columns and dimensions
Test files	Comprehensive test coverage for vector functionality, type mapping, and query translation

Files not reviewed (1)

• src/EFCore.SqlServer/Properties/SqlServerStrings.Designer.cs: Language not supported