Update to .NET 9 and latest version of dependencies

[jasonjoh]

No description provided.

[Copilot]

Pull Request Overview

This PR updates the project from .NET 8 to .NET 9 and upgrades various NuGet dependencies to their latest versions. The changes also include updates to the OpenAPI library usage to align with the new major version.

• Upgrade target framework from .NET 8.0 to .NET 9.0 across all projects
• Update NuGet packages including Microsoft.OpenApi from v1.6.24 to v2.0.0 and System.CommandLine to latest beta
• Refactor code to use new Microsoft.OpenApi v2.0 APIs and System.CommandLine syntax

Reviewed Changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
src/CheckCloudSupport.csproj	Updates target framework to .NET 9.0 and upgrades package references
test/CheckCloudSupportTests.csproj	Updates target framework to .NET 9.0 and test SDK packages
src/Program.cs	Refactors System.CommandLine usage and OpenApi reader API calls for v2.0 compatibility
src/Extensions/OpenApiUrlTreeNodeExtensions.cs	Updates OpenApi namespace usage and removes deprecated helper method
.vscode/launch.json	Updates debug configuration paths to use .NET 9.0 build outputs
.github/workflows/dotnet.yml	Updates CI workflow to use .NET 9.x

Comments suppressed due to low confidence (1)

src/CheckCloudSupport.csproj:25

• The version '2.0.0-beta6.25358.103' appears to be invalid. System.CommandLine beta versions typically follow the pattern '2.0.0-beta4.22272.1'. Please verify this version exists in the NuGet repository.

    <PackageReference Include="System.CommandLine" Version="2.0.0-beta6.25358.103" />