Move two symbol diagnostics in [ObservableProperty] generator to analyzers

[Sergio0694]

Describe the bug

I've missed a couple of IncrementalValuesProvider<ISymbol> in the observable property generator, which should definitely move to the analyzer now that that's in place instead. Should make the generator a bit faster and also reduce memory use.

dotnet/src/CommunityToolkit.Mvvm.SourceGenerators/ComponentModel/ObservablePropertyGenerator.cs

Lines 118 to 122 in 302b8a9

	IncrementalValuesProvider<INamedTypeSymbol> classSymbols =
	context.SyntaxProvider
	.CreateSyntaxProvider(
	static (node, _) => node is ClassDeclarationSyntax { AttributeLists.Count: > 0 },
	static (context, _) => (INamedTypeSymbol)context.SemanticModel.GetDeclaredSymbol(context.Node)!);

Nuget packages

• CommunityToolkit.Common
• CommunityToolkit.Diagnostics
• CommunityToolkit.HighPerformance
• CommunityToolkit.Mvvm (aka MVVM Toolkit)