Implement Software Keyboard GTK frontend (#1434)

* Implement SwKbd GUI

* Relocate UI handler to Emu Context from Config

Also create a common interface for UI handlers in the context and specialize for Gtk

Add basic input length validation in InputDialog

* Add Transfer Memory support to AppletCreator

Read Initial Text for SwKbd using Transfer Memory

* Improve InputDialog widget

Improve length validation
Has extra label to show validition info
Handle potential errors and log them

* Misc improvements

* Improve string validation
* Improve error handling
* Remove tuple in struct
* Address formatting nits

* Add proper Cancel functionality

Also handle GUI errors in UI handler

* Address jD's comments

* Fix _uiHandler init

* Address AcK's comments

Ryujinx.HLE/Switch.cs

@@ -37,6 +37,8 @@ namespace Ryujinx.HLE
 
         public Hid Hid { get; private set; }
 
+        public IHostUiHandler UiHandler { get; set; }
+
         public bool EnableDeviceVsync { get; set; } = true;
 
         public Switch(VirtualFileSystem fileSystem, ContentManager contentManager, IRenderer renderer, IAalOutput audioOut)