[Housekeeping] Add ReferenceAssembliesExtensions extension for ReferenceAssemblies.Net.Net100

[TheCodeTraveler]

Description of Change

This PR adds a temporary work-around for Microsoft.CodeAnalysis.Testing.ReferenceAssemblies.Net.Net100 as recommended in the Rosyln GitHub repo: dotnet/roslyn-sdk#1233 (comment)

using Microsoft.CodeAnalysis.Testing;

namespace CommunityToolkit.Maui.Analyzers.UnitTests;

static class ReferenceAssembliesExtensions
{
	static readonly Lazy<ReferenceAssemblies> lazyNet100 = new(() =>
		new(targetFramework: "net10.0",
			referenceAssemblyPackage: new PackageIdentity("Microsoft.NETCore.App.Ref", "10.0.0-rc.2.25502.107"),
			referenceAssemblyPath: Path.Combine("ref", "net10.0")));

	extension(ReferenceAssemblies.Net)
	{
		public static ReferenceAssemblies Net100 => lazyNet100.Value;
	}
}

PR Checklist

• Rebased on top of main at time of PR
• Changes adhere to coding standard

Additional information

This extension member will be removed once Microsoft publishes the next release of Microsoft.CodeAnalysis.CSharp.Analyzer.Testing to NuGet.

Microsoft.CodeAnalysis.Testing.ReferenceAssemblies.Net.Net100 was added to Microsoft.CodeAnalysis.CSharp.Analyzer.Testing in this PR: dotnet/roslyn-sdk#1221.

This PR also re-enables in build.yml the Run CommunityToolkit Analyzers UnitTests step.