tests: cpp: cxx: Test with various types of libc

This commit changes the C++ subsystem test, which previously was only
being run with the minimal libc, to be run with all the mainstream C
libraries (minimal libc, newlib, newlib-nano, picolibc).

Signed-off-by: Stephanos Ioannidis <root@stephanos.io>
(cherry picked from commit 03f06931)