After this upgrade, it's save to pretend we never had 32-bit integers: depart from me.
This keeps the node codebase clean, and we pretend like we always had 63+sign-bit integers.
We don't update agora's defaults etc., which can be done in a separate diff.
Also, feature_63_bit_ints is removed because this is a test just for the activation, which ostensibly worked very well.