Allow passing children to ListAction component

[WiXSL]

In order to add custom actions to the List component, one has to replace the entire default ´ListActions´ component with something else.

Couldn't it be possible to re-use react-admin's ListActions component and pass children to it?

[fzaninotto]

As explained in #6218, I don't think this is a good idea. I agree that the current way of overriding the List actions isn't very user friendly, but the solution that you propose isn't a clear win and brings confusion.

[fzaninotto]

Fixe by #6218