Import capsicum-test into ^/vendor/google/capsicum-test/dist

The following change imports google/capsicum-test@9333154 from GitHub, omitting
the embedded version of googletest, as well as the incomplete libcasper.

This test suite helps verify capsicum(3) support via functional tests
written in the GoogleTest test framework.

Kernel support for capsicum(4) is tested by side-effect of testing
capsicum(3).

NB: as discussed in a previous [closed] PR [1], the casper(3) tests are
incomplete/buggy and will not pass on FreeBSD. Thus, I have no intention of
integrating them into the build/test on FreeBSD as-is.

The import command used was:

curl -L https://github.com/google/capsicum-test/tarball/9333154 | tar --strip-components=1 -xvzf - -C dist/
rm -Rf dist/*/

1. https://github.com/google/capsicum-test/pull/26

Reviewed by: emaste (mentor)
Differential Revision: https://reviews.freebsd.org/D19261