…t462, net8.0, net10.0

BREAKING CHANGE: Dropped net6.0 and net9.0 target frameworks. Added netstandard2.1,
net8.0, and net10.0. Updated MAUI targets from net6.0-* to net8.0-*.
Downgraded xunit.runner.visualstudio to 2.5.8 for net462 test compatibility.
Added conditional compilation directives for net462 test compatibility.

Closes #1030

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

…ecated macos

- Update MAUI platform targets from net6.0-* to net10.0-* in Directory.Build.props
- Remove net6.0-macos target (deprecated, covered by maccatalyst)
- Remove dead #elif MACOS code path in GraphClientFactory.cs
- Remove 'macos' from workload install in CI pipelines

The net6.0-macos workload no longer exists in modern .NET SDKs, and the
net6.0-* MAUI platform targets are incompatible with the .NET 10 SDK
used in CI. The base net6.0 TFM is preserved for non-MAUI consumers.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Windows-latest now resolves to Windows Server 2025, providing better
alignment with the .NET 10 SDK and modern MAUI workloads.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

.NET 6 is no longer needed - the project targets net8.0 and net10.0.
Updated SDK install to match the actual target frameworks.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

…works

feat!: update target frameworks to netstandard2.0, netstandard2.1, net462, net8.0, net10.0

Update all direct NuGet package dependencies to their latest versions:

- Kiota packages: 1.22.1 → 2.0.0
- Microsoft.IdentityModel packages: 8.16.0 → 8.18.0
- Microsoft.SourceLink.GitHub: 8.0.0 → 10.0.203
- System.Net.Http.WinHttpHandler: 9.0.14 → 10.0.7
- Microsoft.NET.Test.Sdk: 17.13.0 → 18.5.1
- coverlet packages: 6.0.4 → 10.0.0
- Microsoft.VisualStudio.Threading.Analyzers: 17.13.2 → 17.14.15
- xunit.runner.visualstudio: 2.5.8 → 2.8.2 (pinned for net462)

Adapt to Kiota 2.0 breaking changes:

- Replace IAsyncParseNodeFactory with IParseNodeFactory
- Update AsyncMonitor, ResponseHandler, DeltaResponseHandler, UploadResponseHandler
  to use direct IParseNodeFactory instead of casting

BREAKING CHANGE: Kiota upgraded to 2.0.0 which removes IAsyncParseNodeFactory interface.
Internal implementation changes required in response handlers.

feat!: upgrade Kiota to 2.0.0 and support packages

…--main--components--Microsoft.Graph.Core

chore(main): release 4.0.0