Turn ColorSelectorSliders into robust xaml + add hex color field to color sliders

Robust.Client/UserInterface/Controls/AlphaSliderChannel.xaml

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+<BoxContainer xmlns="https://spacestation14.io"
+    Orientation="Horizontal"
+    SeparationOverride="3">
+    <Label Name="ChannelLabel"
+        Text="{Loc 'color-selector-sliders-alpha'}" />
+    <Slider Name="AlphaSlider"
+        HorizontalExpand="True"
+        VerticalAlignment="Center"
+        MaxValue="1.0" />
+    <SpinBox Name="InputBox" />
+</BoxContainer>

Robust.Client/UserInterface/Controls/AlphaSliderChannel.xaml.cs

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+using System;
+using Robust.Client.AutoGenerated;
+using Robust.Client.UserInterface.XAML;
+
+namespace Robust.Client.UserInterface.Controls;
+
+[GenerateTypedNameReferences]
+[Access(typeof(ColorSelectorSliders))]
+public sealed partial class AlphaSliderChannel : BoxContainer, ISliderChannel
+{
+    public event Action<Range>? OnSliderValueChanged;
+    public event Action<ValueChangedEventArgs>? OnSpinValueChanged;
+
+    public Func<int, bool>? IsInputValid
+    {
+        set => InputBox.IsValid = value;
+    }
+
+    public float Value
+    {
+        get => AlphaSlider.Value;
+        set => AlphaSlider.Value = value;
+    }
+
+    public AlphaSliderChannel()
+    {
+        RobustXamlLoader.Load(this);
+        AlphaSlider.OnValueChanged += v => OnSliderValueChanged?.Invoke(v);
+        InputBox.ValueChanged += args => OnSpinValueChanged?.Invoke(args);
+        InputBox.InitDefaultButtons();
+    }
+
+    public void OverrideValue(float value, float divisor)
+    {
+        AlphaSlider.SetValueWithoutEvent(value);
+        InputBox.OverrideValue((int)(value * divisor));
+    }
+}

Robust.Client/UserInterface/Controls/ColorSelectorSliders.xaml

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+<Control xmlns="https://spacestation14.io">
+    <BoxContainer Name="RootBox" Orientation="Vertical">
+        <BoxContainer Name="HeaderBox"
+            Orientation="Horizontal"
+            SeparationOverride="5">
+            <OptionButton Name="TypeSelector" />
+            <Label Name="ColorDescriptionLabel" />
+        </BoxContainer>
+        <BoxContainer Name="BodyBox" Orientation="Vertical">
+            <ColorSliderChannel Name="TopChannel" />
+            <ColorSliderChannel Name="MiddleChannel" />
+            <ColorSliderChannel Name="BottomChannel" />
+            <AlphaSliderChannel Name="AlphaChannel" />
+        </BoxContainer>
+        <BoxContainer Name="HexBox"
+            Orientation="Horizontal"
+            HorizontalExpand="True">
+            <PanelContainer Name="ColorPreviewPanel"
+                Margin="2"
+                HorizontalExpand="True"
+                SizeFlagsStretchRatio="1" />
+            <Control HorizontalExpand="True"
+                SizeFlagsStretchRatio="3" />
+            <BoxContainer Name="HexEditBox" Orientation="Horizontal">
+                <Label Text="#" />
+                <!-- mono line edit added in c# -->
+            </BoxContainer>
+        </BoxContainer>
+    </BoxContainer>
+</Control>