Refactor (NGAP): adopt TO_ENUM/TO_TEXT pattern for NGAP enums

TO_ENUM/TO_TEXT are already used in NAS, and can be adopted in NGAP.
To avoid duplication, the following changes are introduced:

* Move text_info_t, TO_ENUM, TO_TEXT to common/utils/utils.h
* Include utils.h include to ngap_messages_types.h, fgs_nas_utils.h, and fgmm_lib.h
* RRC establishment cause: refactor to FOREACH_RRC_ESTABLISHMENT_CAUSE macro
* Cause Group: refactor to FOREACH_CAUSE_GROUP macro
* Radio Network Cause: refactor to FOREACH_CAUSE_RADIO_NETWORK macro
* Protocol Cause: refactor to FOREACH_CAUSE_PROTOCOL macro

This change is preparatory to the introduction the paging lib with unit
tests, with the goal of reducing the inter-dependency between concurrent
NGAP libs.

common/utils/utils.h

@@ -109,6 +109,15 @@ int hex_char_to_hex_value (char c);
 // Converts an hexadecimal ASCII coded string into its value.**
 int hex_string_to_hex_value (uint8_t *hex_value, const char *hex_string, int size);
 
+/* Map task id to printable name. */
+typedef struct {
+  int id;
+  char text[256];
+} text_info_t;
+
+#define TO_TEXT(LabEl, nUmID) {nUmID, #LabEl},
+#define TO_ENUM(LabEl, nUmID) LabEl = nUmID,
+
 char *itoa(int i);
 
 #define STRINGIFY(S) #S