Avalonia: Clean up leftover RenderTimer & Fix minimum and initial window size (#3935)

* ava: Cleanup RenderTimer

* ava: Remove ContentControl from RendererHost

* ava: Remove unused actual scale factor

* ava: Enable UseGpu for Linux

* ava: Set better initial size & Scale the window properly

* ava: Realign properties

* ava: Use explicit type & specify where the note applies

Ryujinx.Ava/Ui/Windows/MainWindow.axaml

@@ -13,7 +13,7 @@
     Title="Ryujinx"
     Width="1280"
     Height="785"
-    MinWidth="1024"
+    MinWidth="1092"
     MinHeight="680"
     d:DesignHeight="720"
     d:DesignWidth="1280"
@@ -57,6 +57,8 @@
                 <RowDefinition Height="Auto" />
             </Grid.RowDefinitions>
             <StackPanel
+                Name="MenuBar"
+                MinHeight="35"
                 Grid.Row="0"
                 Margin="0"
                 HorizontalAlignment="Stretch"
@@ -549,6 +551,7 @@
             <Grid
                 Name="StatusBar"
                 Grid.Row="2"
+                MinHeight="30"
                 Height="30"
                 Margin="0,0"
                 HorizontalAlignment="Stretch"