trivial: move a couple of functions to nm-ip[46]-config

Note that this patch doesn't effectively change any code.

Functions moved from nm-system:

* nm_system_apply_ip?_config → nm_ip?_config_commit
* ip?_dest_in_same_subnet → nm_ip?_config_destination_is_direct

Functions moved from NetworkManagerUtils:

* nm_utils_merge_ip?_config → nm_ip?_config_merge_setting

Functions renamed (and moved down to form one group):

* nm_ip?_config_new_for_interface → nm_ip?_config_capture

(The rationale for the rename is that from the achitectural point of
view it doesn't matter whether the function creates a new object or
updates an existing one. After the rename, it's obvious that
nm_ip?_config_capture() and nm_ip?_config_commit() are counterparts of
each other.)

src/NetworkManagerUtils.h

@@ -36,9 +36,6 @@ gboolean nm_ethernet_address_is_valid (const struct ether_addr *test_addr);
 
 int nm_spawn_process (const char *args);
 
-void nm_utils_merge_ip4_config (NMIP4Config *ip4_config, NMSettingIP4Config *setting);
-void nm_utils_merge_ip6_config (NMIP6Config *ip6_config, NMSettingIP6Config *setting);
-
 gboolean nm_match_spec_string (const GSList *specs, const char *string);
 gboolean nm_match_spec_hwaddr (const GSList *specs, const char *hwaddr);
 gboolean nm_match_spec_s390_subchannels (const GSList *specs, const char *subchannels);