Provide a standardized way to handle the C++ "standard" headers
customized to be used with current CMake C++ standard constraints.
Offer under directory `cm` headers which can be used as direct
replacements of the standard ones. For example:
#include <cm/string_view>
can be used safely for CMake development in place of the `<string_view>`
standard header.
Fixes: #19491
Enables the clang-tidy test performance-inefficient-string-concatenation
and replaces all inefficient string concatenations with `cmStrCat`.
Closes: #19555
