cmake: sca: Add Parasoft C++test

This commit adds Parasoft C++test as a Static Analyser using Zephyr's SCA
framework.

By specifing -DZEPHYR_SCA_VARIANT=cpptest to west build, a cpptestscan.bdf
file will be generated under builddir/sca/cpptest/.

Signed-off-by: Yasushi SHOJI <yashi@spacecubics.com>