Int fflonk

[swasilyev]

Critical things:

1. get subgroup checks back
2. how to generate an array of 128-bit field elements with merlin
3. Merlin's fsrng is also suspicious

On fflonk side:

1. make commitment affine
2. try remove generic params from keys
3. do subgroup checks?
4. get prepared vk back

Also:

• remove mod kzg
• get back some stupid checks of urs size