ScrollView.ScrollToAsync doesn't work when called from Page.OnAppearing - fix

[kubaflo]

Issues Fixed

Fixes #26781

<Grid RowDefinitions="*,*">
    <ScrollView x:Name="scrollView">

        <VerticalStackLayout>
            <Label Text="This is a scroll view scrolled to the bottom button"
                    HeightRequest="500"/>
            <Button x:Name="BottomButton"
                    AutomationId="successButton"
                    Text="Success if visible"/>
        </VerticalStackLayout>
    </ScrollView>
    <ScrollView Grid.Row="1"
                x:Name="scrollView2">
        <VerticalStackLayout>
            <Label Text="This is a scroll view scrolled to y pos"
                    HeightRequest="500"/>
            <Label AutomationId="successLabel"
                    Text="Success if visible"/>
        </VerticalStackLayout>
    </ScrollView>
</Grid>

protected override async void OnAppearing()
{
	await scrollView.ScrollToAsync(BottomButton, ScrollToPosition.MakeVisible, true);
	await scrollView2.ScrollToAsync(0, 600, true);
}

Android	iOS
Screen.Recording.2024-12-24.at.01.51.23.mov	Untitled.mp4

[dotnet-policy-service]

Hey there @kubaflo! Thank you so much for your PR! Someone from the team will get assigned to your PR shortly and we'll get it reviewed.