gained_focus broken for parent Ui

[oleflb]

Describe the bug

gained_focus is broken in some cases. In the given example, has_focus of response becomes true in the same frame that had_focus_last_frame becomes true. Therefore gained_focus is always false.
In the provided example, the text is never printed when pressin the "Focus" button.

Screencast.From.2025-02-19.18-45-56.mp4

To Reproduce
Steps to reproduce the behavior:
Here is some code for reproduction

use eframe::{
    egui::{CentralPanel, Context, Response, Sense, Ui, UiBuilder, Widget},
    run_simple_native, Frame, NativeOptions,
};

fn main() -> Result<(), eframe::Error> {
    run_simple_native("Test", NativeOptions::default(), update)
}

fn update(ctx: &Context, _frame: &mut Frame) {
    CentralPanel::default().show(ctx, |ui| {
        let response = ui.add(SomeWidget);

        if ui.button("Focus").clicked() {
            response.request_focus();
        }
    });
}

pub struct SomeWidget;

impl Widget for SomeWidget {
    fn ui(self, ui: &mut Ui) -> Response {
        ui.scope_builder(UiBuilder::default().sense(Sense::FOCUSABLE), |ui| {
            let response = ui.response();
            let button = ui.button("Button");

            if response.has_focus() && response.gained_focus() {
                println!("Button gained focus");
            }

            if response.gained_focus() {
                button.request_focus();
            }
        })
        .response
    }
}

Expected behavior
I expect gained_focus to be true when has_focus becomes true.

Desktop (please complete the following information):

• OS: Fedora Linux 41
• eframe/egui version: tested on 0.31 and master (native)