testing: add unistd.h and pthread.h headers

Add unistd.h and pthread.h for memorystress_main.c, unistd.h for
dhm.c and cachetest_main.c, and pthread.h for kv_test_019.c to fix
missing declarations.

Signed-off-by: hongfengchen <hongfengchen@xiaomi.com>

examples/mdnsd/mdnsd_daemon.c

@@ -25,7 +25,6 @@
  ****************************************************************************/
 
 #include <nuttx/config.h>
-
 #include <stdint.h>
 #include <stdlib.h>
 

testing/drivers/crypto/dhm.c

@@ -27,6 +27,7 @@
 #include <fcntl.h>
 #include <stddef.h>
 #include <stdio.h>
+#include <unistd.h>
 #include <sys/ioctl.h>
 #include <crypto/cryptodev.h>
 

testing/mm/cachetest/cachetest_main.c

@@ -27,6 +27,7 @@
 #include <nuttx/config.h>
 #include <nuttx/cache.h>
 #include <stdio.h>
+#include <unistd.h>
 #include <syslog.h>
 
 /****************************************************************************

testing/mm/memstress/memorystress_main.c

@@ -28,6 +28,8 @@
 #include <stdlib.h>
 #include <debug.h>
 #include <stdio.h>
+#include <unistd.h>
+#include <pthread.h>
 #include <stddef.h>
 #include <string.h>
 #include <stdint.h>