Add missing cases for Tuple.{Head, Tail, Init, Last}

[nicolasstucki]

All these cases take as input a Tuple but did not handle the empty case.

[sjrd]

I think that was on purpose. We typically want a compile error when trying to get the head of an empty tuple type; not a Nothing.

[nicolasstucki]

This makes more sense in the context of #19185. There we can end up with tup.head of an empty tuple after some steps of reduction. The error that is shown by the match type is worse than the one we can emit in the tuple optimization phase.

Maybe I should do all these changes together.