docs: don't generate <description> tag in "gen-metadata-nm-settings-nmcli"

"gen-metadata-nm-settings-nmcli" previously printed the <description>.
But that tag is not very useful for further processing.

For the most part it itself comes from "src/libnmc-setting/settings-docs.h",
which is generated (but lost formatting information already to be
suitable for where it's used).

Some parts are original texts from "src/libnmc-setting/nm-meta-setting-desc.c",
like TEAM_DESCRIBE_MESSAGE. However those text are also not really suitable
for any other purpose.

Rename the tag, so that the tools that process "gen-metadata-nm-settings-nmcli.xml"
don't use it.

The file "gen-metadata-nm-settings-nmcli.xml" is currently only used to
generate "man/nm-settings-docs-nmcli.xml", and that file slightly
changes with this patch. However, the manual page which is generated by
"man/nm-settings-docs-nmcli.xml" does not change.

src/nmcli/gen-metadata-nm-settings-nmcli.c

@@ -57,10 +57,22 @@ main(int argc, char *argv[])
                 g_print("\n%salias=%s",
                         _indent_level(2 * INDENT + 10),
                         tmp3 = _xml_escape_attribute(prop_info->property_alias));
-            if (prop_info->describe_doc)
-                g_print("\n%sdescription=%s",
+            if (prop_info->describe_doc) {
+                /* These descriptions are used by interactive nmcli modes. For the most part,
+                 * they are themselves generated (see "settings-docs.h"). Some of them are instead
+                 * explicitly (manually) set.
+                 *
+                 * In any case, they serve little purpose outside of nmcli's interactive mode,
+                 * because their formatting/wording would not be suitable.
+                 *
+                 * We generate this XML mainly to generate `man nm-settings-nmcli`, but the
+                 * descriptions in "describe_doc" field are not suitable there.
+                 *
+                 * Name them something else ("<nmcli-description>") which isn't actually used. */
+                g_print("\n%snmcli-description=%s",
                         _indent_level(2 * INDENT + 10),
                         tmp4 = _xml_escape_attribute(prop_info->describe_doc));
+            }
             g_print(" />\n");
         }