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"Removing some outdated compiler conditionals", Hans Johnson, 31 July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/itkCoocurrenceTextureFeaturesImageFilter.hxx

@@ -30,7 +30,7 @@ namespace Statistics
 {
 template <typename TInputImage, typename TOutputImage, typename TMaskImage>
 CoocurrenceTextureFeaturesImageFilter<TInputImage, TOutputImage, TMaskImage>::CoocurrenceTextureFeaturesImageFilter()
-  : m_NumberOfBinsPerAxis(itkGetStaticConstMacro(DefaultBinsPerAxis))
+  : m_NumberOfBinsPerAxis(Self::DefaultBinsPerAxis)
   , m_HistogramMinimum(NumericTraits<PixelType>::NonpositiveMin())
   , m_HistogramMaximum(NumericTraits<PixelType>::max())
   , m_InsidePixelValue(NumericTraits<MaskPixelType>::OneValue())

include/itkRunLengthTextureFeaturesImageFilter.hxx

@@ -30,7 +30,7 @@ namespace Statistics
 {
 template <typename TInputImage, typename TOutputImage, typename TMaskImage>
 RunLengthTextureFeaturesImageFilter<TInputImage, TOutputImage, TMaskImage>::RunLengthTextureFeaturesImageFilter()
-  : m_NumberOfBinsPerAxis(itkGetStaticConstMacro(DefaultBinsPerAxis))
+  : m_NumberOfBinsPerAxis(Self::DefaultBinsPerAxis)
   , m_HistogramValueMinimum(NumericTraits<PixelType>::NonpositiveMin())
   , m_HistogramValueMaximum(NumericTraits<PixelType>::max())
   , m_HistogramDistanceMinimum(NumericTraits<RealType>::ZeroValue())