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
These new capabilities enable to manage link directories
Two new properties:
* target properties: LINK_DIRECTORIES and INTERFACE_LINK_DIRECTORIES
One new command
* target_link_directories(): to populate target properties
Fixes: #17215
