lib: cpp: Introduce FULL_LIBCPP_SUPPORTED similar to C version

Introduce Kconfig symbol FULL_LIBCPP_SUPPORTED that is similar to the
C version FULL_LIBC_SUPPORTED.  This way we can utilize the same
pattern in tests and samples to filter for when a full libc++ is
needed.

Signed-off-by: Kumar Gala <kumar.gala@intel.com>