ENH: upgrade to use some C++17 constructs

- 'if constexpr (...)'
   * instead of std::enable_if
   * terminate template recursion
   * compile-time elimination of code

- use C++14 '_t', '_v' versions,
  eg, std::is_integral_v<T> instead of std::is_integral<T>::value

- std::begin, std::end, std::void_t instead of prev stdFoam versions

- provide is_contiguous_v<..> as short form of is_contiguous<..>::value
  with the additional benefit of removing any cv qualifiers.

ENH: include is_rotational_vectorspace trait

- tests for vector-space and nComponents > 1 (ie, not sphericalTensor)

ENH: improve robustness of pTraits_.. tests by removing cv qualifiers

applications/test/boolVector/Test-boolVector.C

@@ -5,7 +5,7 @@
     \\  /    A nd           | www.openfoam.com
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
-    Copyright (C) 2020-2022 OpenCFD Ltd.
+    Copyright (C) 2020-2025 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -54,7 +54,7 @@ int main(int argc, char *argv[])
 {
     Info<< "boolVector" << nl
         << "  size = " << boolVector::size() << nl
-        << "  contiguous = " << is_contiguous<boolVector>::value << nl
+        << "  contiguous = " << is_contiguous_v<boolVector> << nl
         << nl;
 
     {