STYLE: Add itkVirtualGetNameOfClassMacro + itkOverrideGetNameOfClassMacro

Added two new macro's, intended to replace the old 'itkTypeMacro' and
'itkTypeMacroNoParent'.

The main aim is to be clearer about what those macro's do: add a virtual
'GetNameOfClass()' member function and override it. Unlike 'itkTypeMacro',
'itkOverrideGetNameOfClassMacro' does not have a 'superclass' parameter, as it
was not used anyway.

Note that originally 'itkTypeMacro' did not use its 'superclass' parameter
either, looking at commit 699b66cb04d410e555656828e8892107add38ccb, Will
Schroeder, June 27, 2001:
https://github.com/InsightSoftwareConsortium/ITK/blob/699b66cb04d410e555656828e8892107add38ccb/Code/Common/itkMacro.h#L331-L337

Author: hjmjohnson

include/itkOpenSlideImageIO.h

@@ -64,7 +64,7 @@ class IOOpenSlide_EXPORT OpenSlideImageIO : public ImageIOBase
   itkNewMacro(Self);
 
   /** Run-time type information (and related methods). */
-  itkTypeMacro(OpenSlideImageIO, ImageIOBase);
+  itkOverrideGetNameOfClassMacro(OpenSlideImageIO);
 
   using ArrayOfExtensionsType = Superclass::ArrayOfExtensionsType;
 

include/itkOpenSlideImageIOFactory.h

@@ -52,7 +52,7 @@ class IOOpenSlide_EXPORT OpenSlideImageIOFactory : public ObjectFactoryBase
   static OpenSlideImageIOFactory* FactoryNew() { return new OpenSlideImageIOFactory;}
 
   /** Run-time type information (and related methods). */
-  itkTypeMacro(OpenSlideImageIOFactory, ObjectFactoryBase);
+  itkOverrideGetNameOfClassMacro(OpenSlideImageIOFactory);
 
   /** Register one factory of this type  */
   static void RegisterOneFactory()