Use Functional::VectorType only if USE_OLD_TNNMG is set

Otherwise use Functional::Vector
3 jobs for minor-updates in 8 minutes and 42 seconds (queued for 2 seconds)
Status Name Job ID Coverage
  Test
passed dune:git clang C++17 #89143

00:06:40

passed dune:git gcc-6 C++14 #89145

00:07:16

passed dune:git gcc-8 C++17 #89144

00:08:42