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 .

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 .

MFC after: 1 month
Sponsored by: EMC / Isilon Storage Division

- Use attach_md instead of hardcoding md(4) provider unit numbers
- Implement a gmirror_test_cleanup function, which in turn calls
geom_test_cleanup to clean up all md(4) providers allocated in the test
run.
- Remove duplicate logic in test scripts for removing md(4) providers.
- Don't create files in /tmp (outside the kyua sandbox); use the current
directory instead

MFC after: 3 weeks
Sponsored by: EMC / Isilon Storage Division

- Make use of geom_subr.sh to improve regression tests.
- Keep class-specific data in conf.sh file.

Convert gmirror(8) regression tests to the new framework.