Move tests to their appropriate source folder

features/FEATURE_IPV4/TESTS/mbedmicro-net/nist_internet_time_service/main.cpp

@@ -1,3 +1,7 @@
+#if !FEATURE_IPV4
+    #error [NOT_SUPPORTED] IPV4 not supported for this target
+#endif
+
 #include "mbed.h"
 #include "LWIPInterface.h"
 #include "UDPSocket.h"

features/FEATURE_IPV4/TESTS/mbedmicro-net/tcp_client_echo/main.cpp

@@ -1,3 +1,7 @@
+#if !FEATURE_IPV4
+    #error [NOT_SUPPORTED] IPV4 not supported for this target
+#endif
+
 #include "mbed.h"
 #include "LWIPInterface.h"
 #include "TCPSocket.h"

features/FEATURE_IPV4/TESTS/mbedmicro-net/tcp_client_hello_world/main.cpp

@@ -1,3 +1,7 @@
+#if !FEATURE_IPV4
+    #error [NOT_SUPPORTED] IPV4 not supported for this target
+#endif
+
 #include <algorithm>
 #include "mbed.h"
 #include "LWIPInterface.h"

features/FEATURE_IPV4/TESTS/mbedmicro-net/udp_echo_client/main.cpp

@@ -1,3 +1,7 @@
+#if !FEATURE_IPV4
+    #error [NOT_SUPPORTED] IPV4 not supported for this target
+#endif
+
 #include "mbed.h"
 #include "LWIPInterface.h"
 #include "UDPSocket.h"