sh: Don't hardcode relative paths in the tests stderr files.

These paths have had to be adjusted to changes in the testsuite runner
several times, so modify the tests to remove the need for such adjustment.

A cp in functional_test.sh is now unneeded, but this matters little in
performance.

Convert bin/sh/tests to ATF

The new code uses a "test discovery mechanism" to determine
what tests are available for execution

The test shell can be specified via:

kyua test -v test_suites.FreeBSD.bin.sh.test_shell=/path/to/test/sh

Sponsored by: EMC / Isilon Storage Division
Approved by: jmmv (mentor)
Reviewed by: jilles (maintainer)

Migrate tools/regression/bin/ tests to the new layout.

This change is a proof of concept on how to easily integrate existing
tests from the tools/regression/ hierarchy into the /usr/tests/ test
suite and on how to adapt them to the new layout for src.

To achieve these goals, this change:

- Moves tests from tools/regression/bin/<tool>/ to bin/<tool>/tests/.
- Renames the previous regress.sh files to legacy_test.sh.
- Adds Makefiles to build and install the tests and all their supporting
data files into /usr/tests/bin/.
- Plugs the legacy_test test programs into the test suite using the new
TAP backend for Kyua (appearing in 0.8) so that the code of the test
programs does not have to change.
- Registers the new directories in the BSD.test.dist mtree file.

Reviewed by: freebsd-testing
Approved by: rpaulo (mentor)