Add custom refresh rate mode to VSync option (#238)

Rebased @jcm93's refreshinterval branch:
https://github.com/jcm93/Ryujinx/tree/refreshinterval

The option is placed under System/Hacks. Disabled, it's the default
Ryujinx behavior. Enabled, the behavior is shown in the attached
screenshots. If a framerate is too high or low, you can adjust the value
where you normally toggle VSync on and off. It will also cycle through
the default on/off toggles.

Also, in order to reduce clutter, I made an adjustment to remove the
target FPS and only show the percentage.

---------

Co-authored-by: jcm <6864788+jcm93@users.noreply.github.com>

src/Ryujinx/UI/Views/Main/MainStatusBarView.axaml

@@ -79,15 +79,59 @@
             MaxHeight="18"
             Orientation="Horizontal">
             <TextBlock
-                Name="VsyncStatus"
+                Name="VSyncMode"
                 Margin="5,0,5,0"
                 HorizontalAlignment="Left"
                 VerticalAlignment="Center"
-                Foreground="{Binding VsyncColor}"
+                Foreground="{Binding VSyncModeColor}"
                 IsVisible="{Binding !ShowLoadProgress}"
-                PointerReleased="VsyncStatus_PointerReleased"
-                Text="VSync"
-                TextAlignment="Start" />
+                PointerReleased="VSyncMode_PointerReleased"
+                Text="{Binding VSyncModeText}"
+                TextAlignment="Start"/>
+                <Button MinWidth="0"
+                        Width="20"
+                        IsVisible="{Binding ShowCustomVSyncIntervalPicker}"
+                        Margin="-5,0,5,0"
+                        Background="Transparent"
+                        BorderThickness="0">
+                    <ui:SymbolIcon Symbol="Settings"
+                                   HorizontalAlignment="Stretch"
+                                   VerticalAlignment="Center"
+                                   Width="14"
+                                   Height="14"/>
+                    <Button.Styles>
+                        <Style Selector=":checked">
+                            <Style Selector="^:checked ContentPresenter">
+                                <Setter Property="Foreground" Value="{DynamicResource ThemeForegroundColor}" />
+                            </Style>
+                        </Style>
+                        <Style Selector="Border#SeparatorBorder">
+                            <Setter Property="Opacity" Value="0" />
+                        </Style>
+                    </Button.Styles>
+                    <Button.Flyout>
+                        <Flyout Placement="Top" ShowMode="TransientWithDismissOnPointerMoveAway">
+                            <StackPanel Margin="0,0,0,0"
+                                        Orientation="Horizontal">
+                                <Slider Value="{Binding CustomVSyncIntervalPercentageProxy}"
+                                        MinWidth="175"
+                                        Margin="0,-3,0,0"
+                                        Height="32"
+                                        Padding="0,-5"
+                                        TickFrequency="1"
+                                        IsSnapToTickEnabled="True"
+                                        LargeChange="10"
+                                        SmallChange="1"
+                                        VerticalAlignment="Center"
+                                        Minimum="10"
+                                        Maximum="400" />
+                                <TextBlock Margin="5,0"
+                                           Width="40"
+                                           Text="{Binding CustomVSyncIntervalPercentageText}"/>
+                            </StackPanel>
+                        </Flyout>
+                    </Button.Flyout>
+                </Button>
             <Border
                 Width="2"
                 Height="12"