chore: improve codebase with some clippy suggestions #3071

Job	Run time
Check (stable)	8s
Check no_std	24s
Check (nightly)	1m 11s
List directories for parallelizing tests	3s
Check Documentation	54s
Check Style	8s
Test (stable)	9m 2s
Test assembly	8m 23s
Test (nightly)	17m 51s
Test (cp6_782/)	9s
Test (mnt6_753/)	14s
Test (mnt4_753/)	13m 46s
Test (./ed_on_mnt4_753)	3m 57s
Test (./secp256r1)	55s
Test (./ed_on_mnt4_298)	1m 5s
Test (./ed_on_cp6_782)	1m 36s
Test (./mnt4_298)	3m 55s
Test (./mnt6_298)	5m 23s
Test (./ed_on_bn254)	57s
Test (./bn254)	2m 14s
Test (./secp256k1)	1m 0s
Test (./bw6_761)	3m 49s
Test (./bls12_377)	4m 5s
Test (./grumpkin)	1m 6s
Test (./secp384r1)	1m 22s
Test (./ed_on_bls12_377)	1m 10s
Test (./secq256k1)	1m 8s
Test (./ed25519)	1m 4s
Test (./ed_on_bls12_381)	1m 11s
Test (./ed_on_bw6_761)	54s
Test (./curve25519)	1m 1s
Test (./ed_on_bls12_381_bandersnatch)	1m 2s
Test (./pallas)	1m 26s
Test (./vesta)	1m 12s
Test (./bw6_767)	3m 58s
Test (./bls12_381)	3m 16s
	1h 40m 59s

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