Updated SqlClient to 6.1.1 and other deps and removed workaround for issue #624

[ckadluba]

• Updated SqlClient to 6.1.1 and removed Azure.Identity workaround for issue Security issue in dependency Microsoft.Identity.Client #624
• Updated all dependencies except .NET 9 NuGets
• Bumped major version to 9.0.0

[Copilot]

Pull Request Overview

This PR updates the Serilog.Sinks.MSSqlServer package to version 9.0.0 with major dependency updates, particularly upgrading Microsoft.Data.SqlClient from 5.2.3 to 6.1.1 and removing the Azure.Identity workaround that was previously needed for issue #624.

• Updated Microsoft.Data.SqlClient from 5.2.3 to 6.1.1 and removed Microsoft.Identity.Client dependency
• Upgraded multiple development and testing dependencies including BenchmarkDotNet, FluentAssertions, Moq, and Serilog
• Bumped the package version from 8.2.3 to 9.0.0 to reflect breaking changes

Reviewed Changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.

File	Description
src/Serilog.Sinks.MSSqlServer/Serilog.Sinks.MSSqlServer.csproj	Updated version prefix to 9.0.0 and removed Microsoft.Identity.Client package reference
Directory.Packages.props	Updated versions for SqlClient, testing frameworks, and other dependencies
CHANGES.md	Added changelog entry documenting the major version update and dependency changes

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[Copilot]

The PackageValidationBaselineVersion should be updated to reflect the new major version. Consider updating it to 9.0.0 to maintain consistency with the new VersionPrefix.

Suggested change

	<PackageValidationBaselineVersion>8.0.0</PackageValidationBaselineVersion>
	<PackageValidationBaselineVersion>9.0.0</PackageValidationBaselineVersion>