SQL Server: add support for object in SqlServerConvertTranslator

[imangd]

Fixes #30818

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• Commit messages follow this format:

        Summary of the changes
        - Added support for `object` type arguments for Convert methods in `SqlServerConvertTranslator`

        Fixes #30818

• Tests for the changes have been added (for bug fixes / features)
• Code follows the same patterns and style as existing code in this repo

[imangd]

@dotnet-policy-service agree