Simplify compress_elements

[ljedrz]

This PR is a suggestion for further investigation, so I'm filing it as a draft. It builds on https://github.com/AleoHQ/snarkVM/pull/2150 with the final commit being new.

In compress_elements, which only ever gets called from push_elements_to_sponge, the second tuple members (first.1 and second.1) are always F::one, which means that:

• we don't need to pass tuples from push_elements_to_sponge (only limbs)
• the overhead calculation only needs to be performed once

This is not a viable approach if we want compress_elements to be callable from outside of push_elements_to_sponge etc, but if this is not expected, it would be a simple win for perf and clarity.