SDL3 (#5583)

* Start converting SDL2 backend to SDL3.

Game starts, but a lot of stuff is broken. Oh well.

* Fix text input

SDL3 changed the API somewhat, for the better. Changes all over UI/Clyde/SDL3 layer.

* Fix mouse buttons being broken

* Remove records from SDL3 WSI

The fact that this shaved 2-3% off Robust.Client.dll is mindboggling. Records are so bad.

* Set Windows/X11 native window properties

* Fix window resize events getting wrong size

oops

* Remove "using static" from SDL3 WSI

Seriously seems to hurt IDE performance, oh well.

* Apparently I never called CheckThreadApartment().

* Add STAThreadAttribute to sandbox

Necessary for content start

* Set window title on creation properly.

* Load window icons

* Fix GLFW NoTitleBar style handling

Yeah this PR is supposed to be about SDL3, so what?

* Implement more window creation settings in SDL3

Mostly the ones that need a lot of platform-specific stuff to work.

* Make fullscreen work properly in SDL3.

* File dialogs with SDL3

Removes need for swnfd.

* Fix some TODOs

* Fix WebView build

Robust.Client.WebView/Cef/WebViewManagerCef.Control.cs

@@ -484,27 +484,27 @@ namespace Robust.Client.WebView.Cef
             public void FocusEntered()
             {
                 if (_textInputActive)
-                    _clyde.TextInputStart();
+                    Owner.Root?.Window?.TextInputStart();
             }
 
             public void FocusExited()
             {
                 if (_textInputActive)
-                    _clyde.TextInputStop();
+                    Owner.Root?.Window?.TextInputStop();
             }
 
             public void TextInputStart()
             {
                 _textInputActive = true;
                 if (Owner.HasKeyboardFocus())
-                    _clyde.TextInputStart();
+                    Owner.Root?.Window?.TextInputStart();
             }
 
             public void TextInputStop()
             {
                 _textInputActive = false;
                 if (Owner.HasKeyboardFocus())
-                    _clyde.TextInputStop();
+                    Owner.Root?.Window?.TextInputStop();
             }
 
             private sealed class LiveData