feat: new "unsigned or signed" type, and msm for them #55

Job	Run time
Check Style	8s
Test (nightly)	30s
Check Documentation	55s
List directories for parallelizing tests	4s
Test assembly	49s
Test (mnt6_753/)	1m 6s
Test (cp6_782/)	44s
Test (stable)	28s
Check (nightly)	32s
Check no_std	19s
Check (stable)	28s
Test (mnt4_753/)	47s
Test (./ed_on_bn254)	45s
Test (./mnt6_298)	48s
Test (./mnt4_298)	46s
Test (./bls12_377)	49s
Test (./ed_on_bls12_381)	48s
Test (./grumpkin)	46s
Test (./ed25519)	44s
Test (./bn254)	46s
Test (./curve25519)	46s
Test (./ed_on_bls12_381_bandersnatch)	42s
Test (./ed_on_bls12_377)	46s
Test (./ed_on_mnt4_753)	42s
Test (./secq256k1)	33s
Test (./ed_on_mnt4_298)	41s
Test (./secp384r1)	39s
Test (./bls12_381)	38s
Test (./vesta)	46s
Test (./ed_on_bw6_761)	38s
Test (./secp256k1)	46s
Test (./bw6_767)	38s
Test (./ed_on_cp6_782)	39s
Test (./pallas)	48s
Test (./bw6_761)	40s
Test (./secp256r1)	37s
	24m 1s

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