fix(efcore): generate YDB DELETE ON for ExecuteDelete with joins

[KirillKurdyukov]

Split from #666 — Delete only. ExecuteUpdate / UPDATE ON will follow in a separate PR.

Summary

• Replace unsupported SQL Server-style DELETE FROM with joins with YDB DELETE ON in YdbQuerySqlGenerator.
• Resolve primary key columns for DELETE ON from TableExpression metadata (FindPrimaryKey()), avoiding EF pushdown subqueries.
• Add focused SQL generation tests in ExecuteDeleteSqlYdbTest and a CHANGELOG entry.

Test plan

• dotnet test src/EFCore.Ydb/test/EntityFrameworkCore.Ydb.FunctionalTests/EntityFrameworkCore.Ydb.FunctionalTests.csproj --filter FullyQualifiedName~ExecuteDeleteSqlYdbTest -f net10.0
• CI integration tests against local YDB

Made with Cursor

[codecov-commenter]

Codecov Report

❌ Patch coverage is 37.14286% with 66 lines in your changes missing coverage. Please review.
✅ Project coverage is 82.34%. Comparing base (b71789c) to head (69331bb).

Files with missing lines	Patch %	Lines
...ore.Ydb/src/Query/Internal/YdbQuerySqlGenerator.cs	37.14%	61 Missing and 5 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #667      +/-   ##
==========================================
- Coverage   82.88%   82.34%   -0.55%     
==========================================
  Files         151      151              
  Lines        9389     9492     +103     
  Branches      898      913      +15     
==========================================
+ Hits         7782     7816      +34     
- Misses       1314     1377      +63     
- Partials      293      299       +6     

Flag	Coverage Δ
efcore-ydb	43.01% <37.14%> (-0.08%)	⬇️
ydb-sdk	83.52% <ø> (-0.05%)	⬇️

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