Add batch upsert support for SQL Server Memory DB

[kbeaugrand]

Related to #485

Implements batching upsert functionality in SQL Server Memory DB and updates documentation to reflect the new feature.

• Code Enhancements:

  • Introduces the IMemoryDbBatchUpsert interface in SqlServerMemory.cs to support batch upsert operations.
  • Adds a new method BatchUpsertAsync for handling multiple record upserts in a batch, improving performance for bulk operations.
  • Modifies the UpsertAsync method to internally call BatchUpsertAsync, ensuring consistency in handling single and multiple record upserts.
  • Implements exception handling for batch upsert scenarios, including throwing an IndexNotFoundException when attempting to upsert to a non-existent index.

• Documentation Updates:

  • Updates README.md in the SQL Server extension directory to include information about the new batch upsert feature.
  • Provides examples on how to use the BatchUpsertAsync method for efficient data insertion or updating.

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[dluc]

@kbeaugrand:

Error: SqlServerMemory.cs(377,43): error CS8425: Async-iterator 'SqlServerMemory.BatchUpsertAsync(string, IEnumerable, CancellationToken)' has one or more parameters of type 'CancellationToken' but none of them is decorated with the 'EnumeratorCancellation' attribute, so the cancellation token parameter from the generated 'IAsyncEnumerable<>.GetAsyncEnumerator' will be unconsumed [/home/runner/work/kernel-memory/kernel-memory/extensions/SQLServer/SQLServer/SQLServer.csproj]

https:/microsoft/kernel-memory/actions/runs/9132504455/job/25113991349?pr=489

[kbeaugrand]

@kbeaugrand:

Error: SqlServerMemory.cs(377,43): error CS8425: Async-iterator 'SqlServerMemory.BatchUpsertAsync(string, IEnumerable, CancellationToken)' has one or more parameters of type 'CancellationToken' but none of them is decorated with the 'EnumeratorCancellation' attribute, so the cancellation token parameter from the generated 'IAsyncEnumerable<>.GetAsyncEnumerator' will be unconsumed [/home/runner/work/kernel-memory/kernel-memory/extensions/SQLServer/SQLServer/SQLServer.csproj]

https:/microsoft/kernel-memory/actions/runs/9132504455/job/25113991349?pr=489

Should be fixed now.