ENH: 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 699b66c, Will
Schroeder, June 27, 2001:
https://github.com/InsightSoftwareConsortium/ITK/blob/699b66cb04d410e555656828e8892107add38ccb/Code/Common/itkMacro.h#L331-L337

Modules/Core/Common/include/itkMacro.h

@@ -432,16 +432,22 @@ namespace itk
     ITK_MACROEND_NOOP_STATEMENT
 #endif
 
-/** Macro used to add standard methods to all classes, mainly type
- * information. */
-#define itkTypeMacro(thisClass, superclass)                           \
-  const char * GetNameOfClass() const override { return #thisClass; } \
-  ITK_MACROEND_NOOP_STATEMENT
 
-#define itkTypeMacroNoParent(thisClass)                              \
+/** Macro's used to add `GetNameOfClass()` member functions to polymorphic ITK classes: `itkVirtualGetNameOfClassMacro`
+ * adds a virtual `GetNameOfClass()` member function to the class definition, and `itkOverrideGetNameOfClassMacro` adds
+ * a `GetNameOfClass()` override. */
+#define itkVirtualGetNameOfClassMacro(thisClass)                     \
   virtual const char * GetNameOfClass() const { return #thisClass; } \
   ITK_MACROEND_NOOP_STATEMENT
 
+#define itkOverrideGetNameOfClassMacro(thisClass)                     \
+  const char * GetNameOfClass() const override { return #thisClass; } \
+  ITK_MACROEND_NOOP_STATEMENT
+
+/** Macro used to add standard methods to all classes, mainly type information. */
+#define itkTypeMacro(thisClass, superclass) itkOverrideGetNameOfClassMacro(thisClass)
+#define itkTypeMacroNoParent(thisClass) itkVirtualGetNameOfClassMacro(thisClass)
+
 namespace itk
 {
 /**