Implement 64 bits goldilocks

[diegokingston]

Implement the 64 bits Goldilocks, with $F = 2^64 - 2^32 + 1$

This shouldn't be done with the MontgomeryBackend, and instead should be optimized. NTT shouldn't be implemented before defining how it will be handled with extension fields.

• Implement Goldilocks Field with the specific backend
• Implement degree 2 extension

For reference code:

Plonky 3
Risc Zero

[MauroToscano]

Done