feat(api): added search_recursive prop to menus

[tomasklaen]

search_recursive makes user search look into submenus as well, effectively flattening the menu for the duration of the search.

With this, we don't need a new menu-palette command anymore. It's just built into the default one:

[tomasklaen]

Maybe we should use / as a separator. > doesn't look good in non-monospace fonts, and takes too much space.

[christoph-heinrich]

| might be a good symbol for that, as it takes up even less space and people are less likely to have item titles with it.
But / is a commonly used path separator, so it's good from a semantic pov...

[tomasklaen]

I went with /. It's pretty much a standard to separate categories anywhere.

Also, should it be search_recursive, or search_submenus?

[dyphire]

LGTM

[christoph-heinrich]

search_recursive makes more sense because it doesn't only search submenus, although with the description that shouldn't really be a problem.

search_all maybe? But that's also not good because it doesn't search parent menus.

My personal favorite is search_submenus, even if search_recursive is technically more correct.