Add `asm` feature to curves #3137

Job	Run time
Check no_std	25s
List directories for parallelizing tests	4s
Check (stable)	2m 24s
Check (nightly)	1m 11s
Check Documentation	54s
Check Style	9s
Test (stable)	9m 15s
Test assembly	8m 23s
Test (nightly)	17m 36s
Test (cp6_782/)	27m 1s
Test (mnt4_753/)	15m 20s
Test (mnt6_753/)	21m 52s
Test (./secp256k1)	1m 7s
Test (./mnt6_298)	4m 50s
Test (./ed_on_cp6_782)	1m 14s
Test (./ed_on_bn254)	57s
Test (./secp384r1)	1m 21s
Test (./ed_on_bls12_377)	1m 13s
Test (./bls12_381)	3m 19s
Test (./grumpkin)	1m 25s
Test (./ed_on_bls12_381)	1m 12s
Test (./curve25519)	1m 1s
Test (./ed_on_mnt4_753)	3m 50s
Test (./ed_on_bls12_381_bandersnatch)	1m 11s
Test (./ed25519)	57s
Test (./bls12_377)	3m 58s
Test (./ed_on_bw6_761)	40s
Test (./ed_on_mnt4_298)	1m 4s
Test (./secp256r1)	57s
Test (./mnt4_298)	3m 48s
Test (./secq256k1)	56s
Test (./pallas)	1m 5s
Test (./bw6_761)	3m 41s
Test (./bw6_767)	3m 49s
Test (./bn254)	2m 11s
Test (./vesta)	1m 10s
	2h 31m 30s

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