Add some cases to enumerate all the C++ standard variants that the SDK
gcc supports (there are MANY) to prevent compatibility regressions in
the OS headers.
Signed-off-by: Andy Ross <andyross@google.com>
This commit moves the C++ library tests under `tests/subsys/cpp` to
`tests/lib/cpp` now that the C++ library has been relocated to
`lib/cpp`.
Signed-off-by: Stephanos Ioannidis <stephanos.ioannidis@nordicsemi.no>