Implement new encodings

[b-wagn]

New encodings have been proposed in the aborting RO paper.
We should consider implementing and benchmarking them, especially in combination with leanVM.

I currently think that these can simply be added by implementing a new instance of the message hash trait and using it in combination with the target sum encoding (essentially as described in the paper).

[TomWambsgans]

I will give it a try

[TomWambsgans]

#38