On a Intel(R) Core(TM) i7-8705G CPU @ 3.10GHz, with 32 GB of RAM:

- Before ff:
hash    time:   [927.61 us 927.78 us 927.98 us]

- Previous commit:
hash    time:   [26.495 us 26.503 us 26.512 us]

- New:
hash    time:   [9.8622 us 9.9953 us 10.127 us]

Migrate from BigInt to ff::Fr, remove generic methods

On a Intel(R) Core(TM) i7-8705G CPU @ 3.10GHz, with 32 GB of RAM:

- Old:
hash    time:   [927.61 us 927.78 us 927.98 us]

- New:
hash    time:   [26.495 us 26.503 us 26.512 us]

On a Intel(R) Core(TM) i7-8705G CPU @ 3.10GHz, with 32 GB of RAM:
hash	time:   [927.61 us 927.78 us 927.98 us]