How can I code/write something, for illustration, sort of like:
using namespace memory::std;

for the need that:
Only names from <memory> (like std::unique_ptr, std::shared_ptr, etc.)
become visible, without bringing in the entire std namespace
In other words; could allow using namespace std::memory; or similar syntax
to only expose symbols from a specific header or subset of a namespace.

That’s conceptually like “namespace submodules” or such