Implement arithmetic operators with a macro #14

Job	Run time
Check (stable)	22s
Check no_std	43s
Check (nightly)	1m 18s
List directories for parallelizing tests	3s
Check Documentation	55s
Check Style	11s
Test (stable)	9m 20s
Test assembly	8m 40s
Test (nightly)	18m 9s
Test (cp6_782/)	10s
Test (mnt4_753/)	12s
Test (mnt6_753/)	12s
Test (./ed25519)	1m 3s
Test (./mnt6_298)	5m 45s
Test (./grumpkin)	1m 11s
Test (./ed_on_cp6_782)	1m 23s
Test (./ed_on_mnt4_753)	3m 51s
Test (./ed_on_bw6_761)	42s
Test (./bls12_381)	3m 21s
Test (./ed_on_bls12_381_bandersnatch)	1m 18s
Test (./ed_on_mnt4_298)	1m 7s
Test (./secq256k1)	54s
Test (./bn254)	2m 21s
Test (./mnt4_298)	3m 34s
Test (./secp256r1)	1m 7s
Test (./vesta)	1m 12s
Test (./ed_on_bn254)	1m 4s
Test (./bw6_761)	4m 14s
Test (./curve25519)	1m 20s
Test (./pallas)	1m 8s
Test (./ed_on_bls12_377)	1m 12s
Test (./secp384r1)	1m 30s
Test (./secp256k1)	1m 16s
Test (./ed_on_bls12_381)	1m 13s
Test (./bls12_377)	4m 16s
Test (./bw6_767)	3m 59s
	1h 30m 16s

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