Upgrade to .NET 10 SDK and update libraries

[runceel]

#510

[Copilot]

Pull Request Overview

This PR upgrades the project to use Central Package Management (CPM) by introducing a Directory.Packages.props file, which centralizes all NuGet package version definitions. The key changes include removing version specifications from individual project files and consolidating them in the new central location, along with updating several package versions.

Key changes:

• Introduced Directory.Packages.props with centralized package version management
• Removed version attributes from all <PackageReference> elements across project files
• Updated several package versions (e.g., Microsoft.NET.Test.Sdk to 18.0.0, System.Reactive to 6.1.0)

Reviewed Changes

Copilot reviewed 9 out of 9 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
Directory.Packages.props	New file defining all package versions centrally with CPM enabled
Source/Directory.Build.props	Removed version from Microsoft.SourceLink.GitHub reference
Source/ReactiveProperty.Core/ReactiveProperty.Core.csproj	Removed version from System.ComponentModel.Annotations and obsolete SourceLink update
Source/ReactiveProperty.NETStandard/ReactiveProperty.NETStandard.csproj	Removed versions from package references and obsolete SourceLink update
Source/ReactiveProperty.Platform.Blazor/ReactiveProperty.Platform.Blazor.csproj	Removed version from AspNetCore.Components.Web and obsolete SourceLink update
Source/ReactiveProperty.Platform.WPF/ReactiveProperty.Platform.WPF.csproj	Removed version from Xaml.Behaviors.Wpf and obsolete SourceLink update
Test/ReactiveProperty.Blazor.Tests/ReactiveProperty.Blazor.Tests.csproj	Removed versions from all test-related package references
Test/ReactiveProperty.NETStandard.Tests/ReactiveProperty.NETStandard.Tests.csproj	Removed versions from all test-related package references
Test/ReactiveProperty.WPF.Tests/ReactiveProperty.WPF.Tests.csproj	Removed versions from all test-related package references

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