Add support for "not in"

[victorr99]

As of today, when we want to write not in, we have to wrap the in clause with brackets and add a not or ! before it: !(foo in (2, 4, 6)).

I would like to see the ability to write foo not in (2, 4, 6) which feels way more natural and is easier to read.

Thanks in advance.

[StefH]

#915