UI: Add the ability to change a DualSense/DualShock 4's LED color.

Not functional yet. This is the UI & persistence side of #572.

src/Ryujinx/UI/Views/Input/ControllerInputView.axaml

@@ -4,6 +4,7 @@
     xmlns:ext="clr-namespace:Ryujinx.Ava.Common.Markup"
     xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
     xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
+    xmlns:ui="clr-namespace:FluentAvalonia.UI.Controls;assembly=FluentAvalonia"
     xmlns:controls="clr-namespace:Ryujinx.Ava.UI.Controls"
     xmlns:viewModels="clr-namespace:Ryujinx.Ava.UI.ViewModels.Input"
     xmlns:helpers="clr-namespace:Ryujinx.Ava.UI.Helpers"
@@ -486,6 +487,37 @@
                             </Button>
                         </Grid>
                     </Border>
+                    <Border
+                        BorderBrush="{DynamicResource ThemeControlBorderColor}"
+                        BorderThickness="1"
+                        CornerRadius="5"
+                        HorizontalAlignment="Stretch"
+                        Margin="0,-1,0,0">
+                        <Grid IsVisible="{Binding ParentModel.HasLed}">
+                            <Grid.ColumnDefinitions>
+                                <ColumnDefinition Width="*" />
+                                <ColumnDefinition Width="Auto" />
+                            </Grid.ColumnDefinitions>
+                            <CheckBox
+                                Margin="10"
+                                MinWidth="0"
+                                Grid.Column="0"
+                                IsChecked="{Binding Config.EnableLedChanging, Mode=TwoWay}">
+                                <TextBlock Text="Custom LED color" />
+                            </CheckBox>
+                            <ui:ColorPickerButton 
+                                Grid.Column="1"
+                                Margin="10"
+                                IsMoreButtonVisible="False"
+                                UseColorPalette="False"
+                                UseColorTriangle="False"
+                                UseColorWheel="False"
+                                ShowAcceptDismissButtons="False"
+                                IsAlphaEnabled="False"
+                                Color="{Binding Config.LedColor, Mode=TwoWay}">
+                            </ui:ColorPickerButton>
+                        </Grid>
+                    </Border>
                 </StackPanel>
             </StackPanel>
             <!-- Right Controls -->