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

Use randomly generated device names in testcases via mktemp -u instead of using
the hardcoded device name, "test"

MFC after: 2 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.

Wait a bit after creating device.

Add regression test for "prefer" balance algorithm in MIRROR class.

Add GEOM_MIRROR class which provide RAID1 functionality and has many useful
features. The gmirror(8) utility should be used for control of this class.
There is no manual page yet, but I'm working on it with keramida@.

Many useful tests provided by: simon (thank you!)
Some ideas from: scottl, simon, phk