tests: don't assume getdtablesize () <= 10000000

tests: don't assume getdtablesize () <= 10000000

* modules/cloexec-tests:
* modules/dup2-tests:
* modules/dup3-tests:
* modules/nonblocking-tests:
* modules/posix_spawn_file_actions_addclose-tests:
* modules/posix_spawn_file_actions_adddup2-tests:
* modules/posix_spawn_file_actions_addopen-tests:
* modules/unistd-safer-tests:
Depend on the getdtablesize module.
* tests/test-cloexec.c:
* tests/test-dup-safer.c:
* tests/test-dup2.c:
* tests/test-dup3.c:
* tests/test-fcntl.c:
* tests/test-nonblocking.c:
* tests/test-posix_spawn_file_actions_addclose.c:
* tests/test-posix_spawn_file_actions_adddup2.c:
* tests/test-posix_spawn_file_actions_addopen.c:
Don't assume getdtablesize () <= 10000000.