ff: refactor cubic extension (#881) #3065

Job	Run time
Check (stable)	6s
Check Style	5s
Check Documentation	55s
Check (nightly)	1m 12s
Check no_std	23s
Test (stable)	8m 56s
List directories for parallelizing tests	2s
Test assembly	8m 27s
Test (nightly)	17m 33s
Test (cp6_782/)	10s
Test (mnt4_753/)	15s
Test (mnt6_753/)	14s
Test (./ed_on_mnt4_753)	3m 52s
Test (./secp256r1)	1m 0s
Test (./ed_on_mnt4_298)	1m 10s
Test (./ed_on_cp6_782)	1m 13s
Test (./mnt4_298)	3m 47s
Test (./mnt6_298)	5m 20s
Test (./ed_on_bn254)	56s
Test (./bn254)	2m 13s
Test (./secp256k1)	1m 3s
Test (./bw6_761)	3m 55s
Test (./bls12_377)	4m 10s
Test (./grumpkin)	1m 7s
Test (./secp384r1)	1m 21s
Test (./ed_on_bls12_377)	1m 4s
Test (./secq256k1)	52s
Test (./ed25519)	56s
Test (./ed_on_bls12_381)	1m 24s
Test (./ed_on_bw6_761)	36s
Test (./curve25519)	1m 1s
Test (./ed_on_bls12_381_bandersnatch)	1m 9s
Test (./pallas)	1m 9s
Test (./vesta)	1m 5s
Test (./bw6_767)	3m 54s
Test (./bls12_381)	3m 10s
	1h 25m 45s

Provide feedback