STYLE: Use auto for declaration of variables initialized by New()

[N-Dekker]

Replaced initializations of the form T::Pointer var = T::New() (sometimes starting with typename) with auto var = T::New(), to reduce code redundancy.

In accordance with C++ Core Guidelines, August 19, 2021: "ES.11: Use auto to avoid redundant repetition of type names" https://isocpp.github.io/CppCoreGuidelines/CppCoreGuidelines#Res-auto

Using Notepad++ v8.1.4, Find in Files (Regular expression):

Find what:  typename (\w+)::Pointer[ ]+(\w+) = \1::New\(\);
Replace with:  auto $2 = $1::New\(\);
Filters: itk*.hxx;itk*.h;itk*.cxx

And then again without typename:

Find what:  (\w+)::Pointer[ ]+(\w+) = \1::New\(\);

Corresponds with ITK pull request InsightSoftwareConsortium/ITK#2826