Fix generating mouse (and other) events in wxOSX wxStaticBitmap

Use custom subclass for native static bitmap, to ensure that we call
wxOSXCocoaClassAddWXMethods() for it.

This notably allows to get mouse click events for this control.

Closes #18545.

src/osx/cocoa/statbmp.mm

@@ -32,6 +32,30 @@
 
 #include "wx/osx/private.h"
 
+@interface wxStaticBitmapView : NSImageView
+{
+}
+@end
+
+@implementation wxStaticBitmapView
+
++ (void)initialize
+{
+    static BOOL initialized = NO;
+    if (!initialized)
+    {
+        initialized = YES;
+        wxOSXCocoaClassAddWXMethods( self );
+    }
+}
+
+- (instancetype)initWithFrame:(NSRect)frameRect
+{
+    self = [super initWithFrame:frameRect];
+    return self;
+}
+@end
+
 class wxStaticBitmapCocoaImpl : public wxWidgetCocoaImpl
 {
 public :
@@ -51,7 +75,7 @@ public :
 
     void SetScaleMode(wxStaticBitmap::ScaleMode scaleMode)
     {
-        NSImageView* v = (NSImageView*) m_osxView;
+        wxStaticBitmapView* v = (wxStaticBitmapView*) m_osxView;
 
         NSImageScaling scaling = NSImageScaleNone;
         switch ( scaleMode )
@@ -92,7 +116,7 @@ wxWidgetImplType* wxWidgetImpl::CreateStaticBitmap( wxWindowMac* wxpeer,
                                                    long WXUNUSED(extraStyle))
 {
     NSRect r = wxOSXGetFrameForControl( wxpeer, pos , size ) ;
-    NSImageView* v = [[NSImageView alloc] initWithFrame:r];
+    wxStaticBitmapView* v = [[wxStaticBitmapView alloc] initWithFrame:r];
 
     wxWidgetCocoaImpl* c = new wxStaticBitmapCocoaImpl( wxpeer, v );
     return c;