chore: improve codebase with some clippy suggestions #2984

Job	Run time
Test (stable)	8m 49s
Test (nightly)	17m 37s
Check Style	8s
Check Documentation	1m 4s
Check (stable)	10s
List directories for parallelizing tests	3s
Check (nightly)	1m 23s
Test (cp6_782/)	12s
Test (mnt4_753/)	11s
Test (mnt6_753/)	27m 32s
Check no_std	24s
Test assembly	8m 23s
Test (./ed_on_mnt4_753)	3m 46s
Test (./secp256r1)	58s
Test (./ed_on_mnt4_298)	1m 3s
Test (./ed_on_cp6_782)	1m 24s
Test (./mnt4_298)	4m 0s
Test (./mnt6_298)	5m 25s
Test (./ed_on_bn254)	1m 8s
Test (./bn254)	2m 16s
Test (./secp256k1)	1m 0s
Test (./bw6_761)	4m 5s
Test (./bls12_377)	4m 14s
Test (./grumpkin)	1m 14s
Test (./secp384r1)	1m 25s
Test (./ed_on_bls12_377)	1m 17s
Test (./secq256k1)	1m 5s
Test (./ed25519)	1m 7s
Test (./ed_on_bls12_381)	1m 19s
Test (./ed_on_bw6_761)	35s
Test (./curve25519)	1m 9s
Test (./ed_on_bls12_381_bandersnatch)	1m 1s
Test (./pallas)	1m 10s
Test (./vesta)	1m 15s
Test (./bw6_767)	4m 7s
Test (./bls12_381)	3m 26s
	1h 55m 25s

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