[enhancement]: Add `gr.Success()`

[Paillat-dev]

For reference: #4319

Add gr.Success() similar to gr.Info() and gr.Warning(). This could be useful for small success messages, ex. to state that a file upload was successful. I do not think that the answer given in #4319 is still pertinent given the continously growing and wider usage of gradio. Furthermore this does not seem like a complex change, nor a breaking one.