[Performance] Consider avoiding symbol visitors in source generators

[Youssef1313]

https://github.com/unoplatform/uno/blob/88d7a4024ccdcaa07a6b8cd056ba55ef4e92865e/src/SourceGenerators/Uno.UI.SourceGenerators/NativeCtor/NativeCtorsGenerator.cs#L33-L34

https://github.com/unoplatform/uno/blob/88d7a4024ccdcaa07a6b8cd056ba55ef4e92865e/src/SourceGenerators/Uno.UI.SourceGenerators/DependencyObject/DependencyObjectGenerator.cs#L32-L33

Also doing the same in #6937

Using RegisterForSyntaxNotifications might be more performant. It's not available in Uno.SourceGeneration, unfortunately.

We could:

• Try to implement it for Uno.SourceGeneration.
• Conditionally compile the generators, for Uno keep the existing approach, and for Roslyn use RegisterForSyntaxNotifications. It might be pain though.

From Roslyn Discord:

[jeromelaban]

Let's see what the performance improvements are with some of the latest changes I'm making with https://github.com/unoplatform/uno/pull/9784, and we may be able to remove the use of Uno.SourceGeneration altogether.

[Youssef1313]

Let's see what the performance improvements are with some of the latest changes I'm making with https://github.com/unoplatform/uno/pull/9784, and we may be able to remove the use of Uno.SourceGeneration altogether.

Nice!! It's going to be very great if we could!

[Youssef1313]

@jeromelaban Now that #9784 is merged, was it possible to always use Roslyn generation? Is this issue can be worked on now or should I wait for something?

[jeromelaban]

I still don't know if we'll be able to do this. We'll have let https://github.com/unoplatform/uno/pull/9808 be tested a bit more until we can do something about it.

[Youssef1313]

This doesn't seem to improve performance (https://github.com/unoplatform/uno/pull/9820) for some unknown reason. Let's close