autoconf: use include directives instead of recursing down tests (mos…

…tly)

Only down to tests/zfs-tests/tests, but pull out C programs into the
main Makefile ‒ this means we get correct dependency tracking for all
programs (and parallelise across them)

dist diff:
  -zfs-2.1.99/tests/zfs-tests/tests/stress/
  -zfs-2.1.99/tests/zfs-tests/tests/stress/Makefile.am
  -zfs-2.1.99/tests/zfs-tests/tests/stress/Makefile.in

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Ahelenia Ziemiańska <nabijaczleweli@nabijaczleweli.xyz>
Closes openzfs#13316

tests/zfs-tests/tests/Makefile.am

@@ -1997,4 +1997,4 @@ nobase_dist_datadir_zfs_tests_tests_SCRIPTS += \
 	functional/zvol/zvol_swap/zvol_swap_003_pos.ksh \
 	functional/zvol/zvol_swap/zvol_swap_004_pos.ksh \
 	functional/zvol/zvol_swap/zvol_swap_005_pos.ksh \
-	functional/zvol/zvol_swap/zvol_swap_006_pos.ksh
+	functional/zvol/zvol_swap/zvol_swap_006_pos.ksh