Use actual implementation of Rescue and Schnorr in the STF

[Nashtare]

The current AIR program re-implements the Rescue hash instantiation being used and the custom Schnorr signature, while external crates are ready to be used.
For consistency, ease of use and prevent breaking changes, it would be better to use the actual implementations directly

[Nashtare]

Type conversion back and forth may be a bit heavy / cumbersome without toposware/cheetah#4 being implemented.