Move code for finding/saving default menu links from menu.inc to menu_link module

I'm assuming this would involve API changes as the functions were renamed to the menu_link namespace? Can we document the list of any API changes here in the summary and make sure to get a maintainer's +1? Presumably it should be pretty straightforward. Thanks!

Sadly enough, these are in menu.inc still:

menu_link_get_preferred()
menu_link_get_defaults()
menu_link_rebuild_defaults()

So they don't need renaming :)

Not sure what else we'd want to move.

Okay, since the menu_router patch went in, I took a look at this.

I moved the 3 functions I mentioned already, which doesn't actually affect anything since menu_link is required.

The other two that were specifically about menu links were menu_load_links() and menu_delete_links(), which I renamed to menu_link_load_links_by_menu() and menu_link_delete_links_by_menu(), since that's what they do.

Let's not get crazy with more changes, given that this just would need more time.

#2207893: Convert menu tree building to a service. works on moving many other bits to menu_link.

Created draft change record:
https://drupal.org/node/2208411

I also checked and found no references to menu_load_links() or menu_delete_links() in existing change records.

https://api.drupal.org/api/drupal/core%21lib%21Drupal%21Core%21EventSubs...

This calls menu_link_rebuild_defaults() and others. It's slightly worse calling a function in module than one in /includes.

Feels like menu_link module should have its own subscriber that calls its own methods.

That's issue's in #2256521: [META] New plan, Phase 2: Implement menu links as plugins, including static admin links and views, and custom links with menu_link_content entity, all managed via menu_ui module