Replace ngap_pdu_t with byte_array_t

ngap_pdu_t has the same definition as byte_array_t, so it is
replaced by the latter. This simplify the stack and reduces
duplicated code.

Also, add function create_byte_array to copy from an
existing buffer to a new byte_array_t and replaced
allocCopy with create_byte_array, and adopted
OCTET_STRING_fromBuf whenever possible.

common/utils/ds/byte_array.h

@@ -28,6 +28,13 @@
 #include <stdint.h>
 #include <stdlib.h>
 
+#define FREE_AND_ZERO_BYTE_ARRAY(BA) \
+  do {                               \
+    free_byte_array(BA);             \
+    BA.buf = NULL;                   \
+    BA.len = 0;                      \
+  } while (0)
+
 typedef struct {
   size_t len;
   uint8_t* buf;
@@ -43,5 +50,6 @@ bool eq_byte_array(const byte_array_t* m0, const byte_array_t* m1);
 
 byte_array_t cp_str_to_ba(const char* str);
 char* cp_ba_to_str(const byte_array_t ba);
+byte_array_t create_byte_array(const size_t len, const uint8_t* buffer);
 
 #endif