Incremental generator shouldn't include symbols in the pipeline

### Is there an existing issue for this?

- [X] I have searched the existing issues

### Current Behavior

`TextColorToGenerator` includes symbols in `userGeneratedClassesProvider` and `mauiControlsAssemblySymbolProvider`, then filtered out in `inputs`.

https://github.com/CommunityToolkit/Maui/blob/9925e1074a7fc18f3072f2c79036904758d7b48e/src/CommunityToolkit.Maui.SourceGenerators/Generators/TextColorToGenerator.cs#L28-L84

### Expected Behavior

It's a better idea to not include symbols in the pipeline, ie, filter everything early.

### Steps To Reproduce

N/A

### Link to public reproduction project repository

N/A

### Environment

N/A

### Anything else?

https://github.com/dotnet/roslyn-analyzers/issues/6352