By adding a `sorting_hint` to a menu item, the program will put orphaned items in the relevant (sub)menu instead of in the first menu with a NEW prefix.
Fixes#4393.
* plugin loader(feat): support loading plugins from user defined directories
Extra plugin lookup paths can be set in global reader setting via key
`extra_plugin_paths`. Value of the key can either be a string or an array
of strings.
* build(fix): also purge non-exist plugins on build
* plugin: migrate debug plugin to menu sorter
