r289172:

Refactor the test/ Makefiles after recent changes to bsd.test.mk (r289158) and
netbsd-tests.test.mk (r289151)

- Eliminate explicit OBJTOP/SRCTOP setting
- Convert all ad hoc NetBSD test integration over to netbsd-tests.test.mk
- Remove unnecessary TESTSDIR setting
- Use SRCTOP where possible for clarity

r290254:

Remove unused variable (SRCDIR)

- r263220 Migrate tools/regression/sbin/ to the new tests layout.
- r263222 Add Makefile missed in r263220.
- r263226 Migrate tools/regression/{usr.bin/lastcomm,usr.sbin}/ to the new tests layout.
- r263227 Migrate most of tools/regression/usr.bin/ to the new tests layout.
- r263345 Expand tabs that sneaked in into spaces.
- r263346 Migrate tools/regression/usr.bin/make/ to the new tests layout.
- r263348 Add Makefiles missed in r263346.
- r263351 Migrate tools/regression/usr.bin/pkill/ to the new tests layout.
- r263388 Mark multi_test as requiring /usr/share/dict/words.
- r263814 Fix path to the run.pl script to let these tests run.
- r264742 Prevent building tests when bootstrapping make.

This is 'make tinderbox' clean.

This is a MFC into stable/10 of:
- r257849 Add libatf-c++ to the prebuild libs.
- r257853 Build and install the atf tests.
- r258233 Move all atf directories to the tests mtree.
- r258285 Fix the build of some ATF tests.

This change is "make tinderbox" clean on ref10-amd64 with the default
settings of WITHOUT_TESTS.  It is likely for the WITH_TESTS build to
still be broken because not all relevant changes have been merged yet.