feat: replace TreeView icon.

src/Semi.Avalonia/Controls/TreeView.axaml

@@ -71,8 +71,8 @@
                     Background="Transparent">
                     <PathIcon
                         Name="PART_ExpandIconPath"
-                        Width="{DynamicResource TreeViewItemIconSize}"
-                        Height="{DynamicResource TreeViewItemIconSize}"
+                        Theme="{StaticResource InnerPathIcon}"
+                        Classes="Small"
                         Data="{DynamicResource ExpanderIconData}"
                         Foreground="{DynamicResource TreeViewItemIconDefaultForeground}">
                         <PathIcon.Transitions>

src/Semi.Avalonia/Themes/Shared/TreeView.axaml

@@ -1,7 +1,6 @@
 <ResourceDictionary xmlns="https://github.com/avaloniaui" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">
     <StaticResource x:Key="TreeViewItemDefaultCornerRadius" ResourceKey="SemiBorderRadiusSmall" />
     <x:Double x:Key="TreeViewItemIndent">20</x:Double>
-    <x:Double x:Key="TreeViewItemIconSize">8</x:Double>
     <StaticResource x:Key="ExpanderIconData" ResourceKey="SemiIconTreeTriangleRight" />
     <Thickness x:Key="TreeViewItemIconMargin">8 0</Thickness>
     <Thickness x:Key="TreeViewItemPadding">0 4 8 4</Thickness>