A `FromLuaOwned` derive macro akin to `FromLua`

[sxyazi]

I have a FromLuaOwned derive macro that's like mlua's FromLua, but it calls userdata.take() instead of userdata.borrow().clone().

It saves me from some code duplication - do you think it's worth adding into mlua proper? If one needs it won't have to implement it themselves and deal with creating a separate crate (proc macros need [lib] proc-macro = true).