cli: Convert SSID to a printable form

If SSID is a UTF-8 string, it is printed as it is, but enclosed in quotes.
Otherwise the bytes are converted to hex string (in uppercase).
The added quotes for UTF-8 string allow to disambiguate the two forms.

cli/src/utils.h

@@ -27,6 +27,7 @@
 /* === Functions === */
 int matches (const char *cmd, const char *pattern);
 int next_arg (int *argc, char ***argv);
+char *ssid_to_printable (const char *str, gsize len);
 GArray *parse_output_fields (const char *fields_str, const NmcOutputField fields_array[], GError **error);
 gboolean nmc_terse_option_check (NMCPrintOutput print_output, const char *fields, GError **error);
 void print_fields (const NmcPrintFields fields, const NmcOutputField field_values[]);