STYLE: Replace itkStaticConstMacro with static constexpr

Use static constexpr directly now that C++11 conformance
is required by all compilers.

:%s/itkStaticConstMacro *( *\([^,]*\),[ \_s]*\([^,]*\),\_s*\([^)]*\)) */static constexpr \2 \1 = \3/ge

'itkStaticConstMacro(name, type, value)' became unconditionally
identical to 'static constexpr type name = value' with ITK commit
aec95193ab00e1322039911e1032da00f3a103b6 "ENH: Update compiler macros (#810)",
maekclena, 7 May 2019.

'itkGetStaticConstMacro(name)' became unconditionally identical to
'(Self::name)' with ITK commit 84e490b81e3f3c2b0edb89ae7b9de53bfc52f2b2
"Removing some outdated compiler conditionals", Hans Johnson, 31 July
2010.

Most 'itkStaticConstMacro' calls were removed by ITK commit 5c14741e1e063a132ea7e7ee69c5bd0a4e49af74

Author: hjmjohnson

include/itkTwoImageToOneImageMetric.h

@@ -82,8 +82,8 @@ class TwoImageToOneImageMetric : public SingleValuedCostFunction
 
   /**  Type of the Transform Base class */
   using TransformType = Transform<CoordinateRepresentationType,
-                                  itkGetStaticConstMacro(MovingImageDimension),
-                                  itkGetStaticConstMacro(FixedImageDimension)>;
+                                  Self::MovingImageDimension,
+                                  Self::FixedImageDimension>;
 
   using TransformPointer = typename TransformType::Pointer;
   using InputPointType = typename TransformType::InputPointType;
@@ -97,21 +97,21 @@ class TwoImageToOneImageMetric : public SingleValuedCostFunction
 
   /** Gaussian filter to compute the gradient of the Moving Image */
   using RealType = typename NumericTraits<MovingImagePixelType>::RealType;
-  using GradientPixelType = CovariantVector<RealType, itkGetStaticConstMacro(MovingImageDimension)>;
-  using GradientImageType = Image<GradientPixelType, itkGetStaticConstMacro(MovingImageDimension)>;
+  using GradientPixelType = CovariantVector<RealType, Self::MovingImageDimension>;
+  using GradientImageType = Image<GradientPixelType, Self::MovingImageDimension>;
   using GradientImagePointer = SmartPointer<GradientImageType>;
   using GradientImageFilterType = GradientRecursiveGaussianImageFilter<MovingImageType, GradientImageType>;
   using GradientImageFilterPointer = typename GradientImageFilterType::Pointer;
   using InterpolatorPointer = typename InterpolatorType::Pointer;
 
   /**  Type for the mask of the fixed image. Only pixels that are "inside"
        this mask will be considered for the computation of the metric */
-  typedef SpatialObject<itkGetStaticConstMacro(FixedImageDimension)> FixedImageMaskType;
+  typedef SpatialObject<Self::FixedImageDimension> FixedImageMaskType;
   using FixedImageMaskPointer = typename FixedImageMaskType::Pointer;
 
   /**  Type for the mask of the moving image. Only pixels that are "inside"
        this mask will be considered for the computation of the metric */
-  typedef SpatialObject<itkGetStaticConstMacro(MovingImageDimension)> MovingImageMaskType;
+  typedef SpatialObject<Self::MovingImageDimension> MovingImageMaskType;
   using MovingImageMaskPointer = typename MovingImageMaskType::Pointer;