Return self from despawn_descendants

[Shatur]

What problem does this solve or what need does it fill?

Sometimes you want to despawn all descendants and insert new children. In order to do it you need to do something like this:

let mut entity = commands.entity(entity);
entity.despawn_descendants();
entity.with_children(|parent| {
    // Spawn new children.
});

What solution would you like?

It would be great to return self from despawn_descendants in order to do something like this:

commands.entity(entity).despawn_descendants().with_children(|parent| {
    // Spawn new children.
});

[AnbyKatz]

I wouldn't mind giving this one a go if its alright

[Shatur]

@AnthonyKalaitzis feel free to do it!

[Shatur]

Closed by #8928.