[Bug] PlaceholderColor on Entry does not work when global Span TextColor style is set

[acuntex]

Description

When setting a PlaceholderColor on an Entry while there is a global style for Span setting TextColor, the PlaceholderColor will not work but instead show the TextColor defined in the global style for Span as PlaceholderColor.
I created a repository with a repro: https://github.com/acuntex/XamarinBug_EntryPlaceHolderColor
Here is what has been changed: acuntex/XamarinBug_EntryPlaceHolderColor@74ab16d

Steps to Reproduce

1. Add global style for Span in App.xaml (Application.Resources)

        <Style TargetType="Span">
            <Setter Property="TextColor" Value="Blue" />
        </Style>

2. Add Entry with Placeholder and PlaceholderColor to some View

            <Entry Placeholder="This placeholder should be red but it is blue because of the global Span TextColor style."
                    PlaceholderColor="Red"
                    HorizontalOptions="FillAndExpand"
                    VerticalOptions="CenterAndExpand">
            </Entry>

Expected Behavior

The Placeholder shows the placeholder in the Color defined by PlaceholderColor.

Actual Behavior

The Placeholder shows the placeholder in the Color defined by the global TextColor style of Span.

Basic Information

• Version with issue: 4.7.0.1080
• Last known good version: None
• IDE: Visual Studio for Mac
• Platform Target Frameworks:
  • iOS: 13.5
• Nuget Packages: Xamarin.Forms
• Affected Devices: All iOS Devices

Screenshots

Reproduction Link

https://github.com/acuntex/XamarinBug_EntryPlaceHolderColor/
acuntex/XamarinBug_EntryPlaceHolderColor@74ab16d

Workaround

    public class CustomEntryRenderer: EntryRenderer
    {
        protected override void UpdatePlaceholder()
        {
            UIFont font = UIFont.FromName(Element.FontFamily, (float) Element.FontSize);
            UpdateAttributedPlaceholder(new NSAttributedString(Element.Placeholder, font, Element.PlaceholderColor.ToUIColor(), Element.BackgroundColor.ToUIColor()));
        }
    }