UI: Rename App to RyujinxApp

Add more NotificationHelper methods
Simplify ID copy logic

src/Ryujinx/RyujinxApp.axaml

@@ -0,0 +1,17 @@
+<Application
+    x:Class="Ryujinx.Ava.RyujinxApp"
+    xmlns="https://github.com/avaloniaui"
+    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
+    xmlns:sty="using:FluentAvalonia.Styling">
+    <Application.Resources>
+        <ResourceDictionary>
+            <ResourceDictionary.MergedDictionaries>
+                <MergeResourceInclude Source="/Assets/Styles/Themes.xaml"/>
+            </ResourceDictionary.MergedDictionaries>
+        </ResourceDictionary>
+    </Application.Resources>
+    <Application.Styles>
+        <sty:FluentAvaloniaTheme PreferUserAccentColor="True" PreferSystemTheme="False" />
+        <StyleInclude Source="/Assets/Styles/Styles.xaml" />
+    </Application.Styles>
+</Application>