chore: improve codebase with some clippy suggestions #3008

Job	Run time
Test (stable)	9m 7s
Test (nightly)	17m 32s
List directories for parallelizing tests	4s
Check (stable)	17s
Check Documentation	1m 8s
Check (nightly)	1m 7s
Check Style	10s
Test (mnt4_753/)	13s
Test (mnt6_753/)	8s
Check no_std	40s
Test assembly	8m 27s
Test (cp6_782/)	6s
Test (./ed_on_mnt4_753)	3m 51s
Test (./secp256r1)	59s
Test (./ed_on_mnt4_298)	1m 6s
Test (./ed_on_cp6_782)	1m 14s
Test (./mnt4_298)	4m 1s
Test (./mnt6_298)	5m 35s
Test (./ed_on_bn254)	1m 6s
Test (./bn254)	2m 18s
Test (./secp256k1)	1m 15s
Test (./bw6_761)	3m 47s
Test (./bls12_377)	4m 7s
Test (./grumpkin)	1m 8s
Test (./secp384r1)	1m 29s
Test (./ed_on_bls12_377)	1m 6s
Test (./secq256k1)	54s
Test (./ed25519)	55s
Test (./ed_on_bls12_381)	1m 19s
Test (./ed_on_bw6_761)	39s
Test (./curve25519)	1m 2s
Test (./ed_on_bls12_381_bandersnatch)	1m 0s
Test (./pallas)	1m 4s
Test (./vesta)	1m 13s
Test (./bw6_767)	3m 59s
Test (./bls12_381)	3m 12s
	1h 27m 18s

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