chore: improve codebase with some clippy suggestions #3070

Job	Run time
Check (stable)	14s
Check (nightly)	1m 4s
Check Documentation	52s
List directories for parallelizing tests	2s
Check Style	5s
Test (stable)	8m 58s
Test (mnt4_753/)	12m 24s
Test (nightly)	17m 35s
Check no_std	28s
Test assembly	8m 22s
Test (cp6_782/)	5s
Test (mnt6_753/)	11s
Test (./ed_on_mnt4_753)	3m 48s
Test (./secp256r1)	54s
Test (./ed_on_mnt4_298)	1m 11s
Test (./ed_on_cp6_782)	1m 13s
Test (./mnt4_298)	3m 50s
Test (./mnt6_298)	5m 34s
Test (./ed_on_bn254)	1m 10s
Test (./bn254)	2m 15s
Test (./secp256k1)	1m 1s
Test (./bw6_761)	4m 0s
Test (./bls12_377)	4m 39s
Test (./grumpkin)	1m 6s
Test (./secp384r1)	1m 19s
Test (./ed_on_bls12_377)	1m 4s
Test (./secq256k1)	52s
Test (./ed25519)	59s
Test (./ed_on_bls12_381)	1m 12s
Test (./ed_on_bw6_761)	37s
Test (./curve25519)	1m 0s
Test (./ed_on_bls12_381_bandersnatch)	1m 0s
Test (./pallas)	1m 3s
Test (./vesta)	1m 9s
Test (./bw6_767)	3m 58s
Test (./bls12_381)	3m 15s
	1h 38m 29s

Provide feedback