I guess a lot of you already thought this was the case, but as explained and discussed in MDL-38322 the /local plugins type is now officially our location for generic plugins for Moodle.
Yes it's a silly name but it's too late to worry about that.
This does not mean anything can be thrown in there. It's a last resort when your plugin doesn't fit anywhere else. In particular a lot of the plugins that are now in /local would probably better be in /admin/tools.