Add .NET 10 support

[RicoSuter]

Ref #5216

[RicoSuter]

@lahma it seems that we need to install .NET8/9 as well, right? But this script only installs/ensures the one from global.json. What's the right way to fix this?

[lahma]

@RicoSuter I think you need to adjust here:

NSwag/build/Build.CI.GitHubActions.cs

Lines 49 to 53 in 6db16d7

	var onUbuntu = image.ToString().StartsWith("ubuntu", StringComparison.OrdinalIgnoreCase);
	if (onUbuntu)
	{
	newSteps.Insert(0, new GitHubActionsSetupDotNetStep(["8.0", "9.0"]));
	}

Maybe shouldn't have OS check then. Then run build.cmd to regenerate.