Improve wxSpinCtrl sizing and appearance on macOS

Multiple improvements to wxSpinCtrl/wxSpinButton appearance:

- fixes broken rendering on macOS 26 (clipped borders)

- corrects wxSpinButton sizes (note that NSStepper doesn't dynamically
  adjust to the size it is set to, but renders at a constant size)

- adds typically used margin between the stepper and the text field

- removes unreachable code in wxWindowMac::DoGetBestSize

src/generic/spinctlg.cpp

@@ -49,11 +49,15 @@ wxIMPLEMENT_DYNAMIC_CLASS(wxSpinDoubleEvent, wxNotifyEvent);
 // ----------------------------------------------------------------------------
 
 // The margin between the text control and the spin: the value here is the same
-// as the margin between the spin button and its "buddy" text control in wxMSW
-// so the generic control looks similarly to the native one there, we might
-// need to use different value for the other platforms (and maybe even
-// determine it dynamically?).
+// as the margin between the spin button and its "buddy" text control in wxMSW,
+// and the commonly used spacing on macOS, so the generic control looks
+// similarly to the native one there, we might need to use different value for
+// other platforms (and maybe even determine it dynamically?).
+#ifdef __WXOSX__
+static const wxCoord MARGIN = 4;
+#else
 static const wxCoord MARGIN = 1;
+#endif
 
 #define SPINCTRLBUT_MAX 32000 // large to avoid wrap around trouble
 
@@ -241,6 +245,10 @@ bool wxSpinCtrlGenericBase::Create(wxWindow *parent,
             m_value = AdjustAndSnap(d);
     }
 
+#ifdef __WXOSX__
+    MacClipsToBounds(false);
+#endif
+
     m_textCtrl   = new wxSpinCtrlTextGeneric(this, DoValueToText(m_value), style);
     m_spinButton = new wxSpinCtrlButtonGeneric(this, style);
 

src/osx/spinbutt_osx.cpp

@@ -13,6 +13,7 @@
 
 #include "wx/spinbutt.h"
 #include "wx/osx/private.h"
+#include "wx/osx/private/available.h"
 
 
 wxSpinButton::wxSpinButton()
@@ -80,7 +81,14 @@ bool wxSpinButton::OSXHandleClicked( double WXUNUSED(timestampsec) )
 
 wxSize wxSpinButton::DoGetBestSize() const
 {
-    return wxSize( 16, 24 );
+    if ( WX_IS_MACOS_AVAILABLE(26, 0) )
+    {
+        return wxSize(21, 28);
+    }
+    else
+    {
+        return wxSize(13, 22);
+    }
 }
 
 void wxSpinButton::TriggerScrollEvent(wxEventType scrollEvent)

src/osx/window_osx.cpp

@@ -1061,13 +1061,6 @@ wxSize wxWindowMac::DoGetBestSize() const
                 r.height = 16 ;
             }
             else
-#endif
-#if wxUSE_SPINBTN
-            if ( IsKindOf( CLASSINFO( wxSpinButton ) ) )
-            {
-                r.height = 24 ;
-            }
-            else
 #endif
             {
                 // return wxWindowBase::DoGetBestSize() ;