MFC r293821:

Integrate
tools/regression/geom_{concat,eli,gate,mirror,nop,raid3,shsec,stripe,uzip}
in to the FreeBSD test suite as
tests/sys/geom/class/{concat,eli,gate,mirror,nop,raid3,shsec,stripe,uzip}

The tools/regression/geom and tools/regression/geom_part testcases are being
left alone because both test sets are both currently broken.

The majority of this work was done on ^/user/ngie/more-tests2 . The differences
are as follows:

• tests/sys/geom/class/Makefile.inc is not present; it was inlined into the class's Makefiles for explicitness.
• The testcases officially require root via kyua
• The geom_gate(4) tests don't use the pidfile changes proposed in https://reviews.freebsd.org/D4836 .