all: add support for route type "throw"

After adding support for "blackhole", "unreachable" and "prohibit" route
types, let's also add support for "throw" type. It works basically the
same as the other types, so supporting it seems very straight forward.

https://gitlab.freedesktop.org/NetworkManager/NetworkManager/-/merge_requests/1124

src/libnm-core-impl/nm-setting-ip-config.c

@@ -1390,7 +1390,8 @@ _ip_route_attribute_validate(const char           *name,
                        RTN_LOCAL,
                        RTN_BLACKHOLE,
                        RTN_UNREACHABLE,
-                       RTN_PROHIBIT)) {
+                       RTN_PROHIBIT,
+                       RTN_THROW)) {
             g_set_error(error,
                         NM_CONNECTION_ERROR,
                         NM_CONNECTION_ERROR_INVALID_PROPERTY,
@@ -1494,6 +1495,7 @@ _nm_ip_route_attribute_validate_all(const NMIPRoute *route, GError **error)
     case RTN_BLACKHOLE:
     case RTN_UNREACHABLE:
     case RTN_PROHIBIT:
+    case RTN_THROW:
         if (route->next_hop) {
             g_set_error(error,
                         NM_CONNECTION_ERROR,

src/libnm-core-impl/nm-setting-ip4-config.c

@@ -1006,7 +1006,8 @@ nm_setting_ip4_config_class_init(NMSettingIP4ConfigClass *klass)
      *      </listitem>
      *      <listitem>
      *        <para><literal>"type"</literal> - one of <literal>unicast</literal>, <literal>local</literal>, <literal>blackhole</literal>,
-     *          <literal>unavailable</literal>, <literal>prohibit</literal>. The default is <literal>unicast</literal>.</para>
+     *          <literal>unavailable</literal>, <literal>prohibit</literal>, <literal>throw</literal>.
+     *          The default is <literal>unicast</literal>.</para>
      *      </listitem>
      *      <listitem>
      *        <para><literal>"window"</literal> - an unsigned 32 bit integer.</para>

src/libnm-core-impl/nm-setting-ip6-config.c

@@ -1042,7 +1042,8 @@ nm_setting_ip6_config_class_init(NMSettingIP6ConfigClass *klass)
      *      </listitem>
      *      <listitem>
      *        <para><literal>"type"</literal> - one of <literal>unicast</literal>, <literal>local</literal>, <literal>blackhole</literal>,
-     *          <literal>unavailable</literal>, <literal>prohibit</literal>. The default is <literal>unicast</literal>.</para>
+     *          <literal>unavailable</literal>, <literal>prohibit</literal>, <literal>throw</literal>.
+     *          The default is <literal>unicast</literal>.</para>
      *      </listitem>
      *      <listitem>
      *        <para><literal>"window"</literal> - an unsigned 32 bit integer.</para>