[T] Added labels to ctests based on subdir in ProcessLib.

Usage:

ctest --print-labels

ctest -L "Steady*|Liquid*" -E LARGE

This runs all benchmarks defined in subdirs starting with Steady OR Liquid
excluding LARGE benchmarks.

Unfortunately AND is not supported in the labels expression yet:

https://gitlab.kitware.com/cmake/cmake/-/issues/21087