Apply clippy suggestions

[Robbepop]

To fix CI and make #573 mergeable.

[paritytech-cicd-pr]

BENCHMARKS

	NATIVE			WASMTIME
BENCHMARK	MASTER	PR	DIFF	MASTER	PR	DIFF	WASMTIME OVERHEAD
execute/ bare_call_0	1.01ms	1.03ms	⚪ 0.68%	1.03ms	934.50µs	🟢 -9.04%	🟢 -10%
execute/ bare_call_0/typed	526.42µs	521.41µs	⚪ -0.97%	453.69µs	447.17µs	🟢 -1.27%	🟢 -14%
execute/ bare_call_1	1.06ms	1.05ms	⚪ 0.07%	1.23ms	1.20ms	🔴 -2.95%	🟢 14%
execute/ bare_call_16	2.10ms	2.12ms	⚪ 1.40%	4.83ms	4.74ms	🔴 -1.51%	🔴 123%
execute/ bare_call_16/typed	1.52ms	1.52ms	⚪ -0.60%	2.30ms	2.42ms	🔴 5.02%	🟡 59%
execute/ bare_call_1/typed	610.49µs	612.59µs	⚪ 0.43%	766.73µs	750.04µs	🟢 -2.66%	🟢 22%
execute/ bare_call_4	1.19ms	1.19ms	⚪ 0.02%	1.97ms	1.90ms	🟢 -3.75%	🟡 59%
execute/ bare_call_4/typed	634.93µs	628.66µs	⚪ -0.85%	909.34µs	910.05µs	⚪ 0.21%	🟢 45%
execute/ br_table	632.72µs	679.97µs	⚪ 2.85%	966.19µs	988.80µs	🔴 2.33%	🟢 45%
execute/ count_until	711.66µs	711.21µs	⚪ 0.00%	2.18ms	2.19ms	⚪ 0.23%	🔴 208%
execute/ factorial_iterative	370.30µs	306.42µs	🟢 -17.32%	866.82µs	866.77µs	⚪ 0.08%	🔴 183%
execute/ factorial_recursive	616.51µs	609.01µs	🟢 -1.29%	1.28ms	1.28ms	⚪ -0.29%	🔴 110%
execute/ fib_iterative	1.49ms	1.44ms	🟢 -3.72%	4.61ms	4.62ms	⚪ 0.21%	🔴 222%
execute/ fib_recursive	5.76ms	5.89ms	⚪ 1.50%	11.81ms	12.03ms	🔴 1.87%	🔴 104%
execute/ global_bump	1.01ms	1.01ms	⚪ -0.21%	3.14ms	3.14ms	⚪ 0.04%	🔴 212%
execute/ global_const	803.88µs	719.62µs	🟢 -10.36%	2.62ms	2.57ms	⚪ -1.11%	🔴 258%
execute/ host_calls	28.84µs	28.99µs	⚪ 0.60%	44.01µs	41.13µs	🟢 -6.38%	🟢 42%
execute/ memory_fill	1.33ms	1.30ms	🟢 -2.04%	4.19ms	4.18ms	⚪ 0.18%	🔴 221%
execute/ memory_sum	1.35ms	1.30ms	🟢 -3.34%	4.23ms	4.23ms	⚪ 0.19%	🔴 225%
execute/ memory_vec_add	2.69ms	2.58ms	🟢 -3.83%	8.47ms	8.47ms	⚪ -0.03%	🔴 228%
execute/ recursive_is_even	1.12ms	1.10ms	⚪ -1.60%	2.10ms	2.09ms	⚪ -0.41%	🟡 91%
execute/ recursive_ok	144.34µs	143.58µs	⚪ -0.27%	310.14µs	297.44µs	🟢 -3.87%	🔴 107%
execute/ recursive_scan	182.42µs	178.30µs	🟢 -2.20%	385.57µs	381.40µs	⚪ -1.08%	🔴 114%
execute/ recursive_trap	14.31µs	14.14µs	⚪ -1.27%	30.09µs	31.09µs	🔴 3.52%	🔴 120%
execute/ regex_redux	548.19µs	548.31µs	⚪ 0.03%	1.51ms	1.53ms	⚪ 1.13%	🔴 178%
execute/ rev_complement	502.61µs	504.26µs	⚪ 0.14%	1.50ms	1.49ms	⚪ -0.06%	🔴 196%
execute/ tiny_keccak	361.80µs	361.51µs	⚪ -0.11%	1.21ms	1.20ms	⚪ -1.17%	🔴 231%
execute/ trunc_f2i	917.23µs	912.90µs	⚪ -0.40%	2.52ms	2.52ms	⚪ -0.23%	🔴 176%
instantiate/ wasm_kernel	60.13µs	59.82µs	⚪ 0.00%	74.41µs	96.43µs	🔴 29.34%	🟡 61%
translate/ erc1155	205.73µs	209.03µs	🔴 1.77%	404.54µs	406.29µs	⚪ 0.00%	🟡 94%
translate/ erc20	102.05µs	102.46µs	⚪ 0.61%	198.56µs	200.31µs	⚪ 0.81%	🟡 95%
translate/ erc721	147.55µs	147.50µs	⚪ 0.46%	287.68µs	289.14µs	⚪ 0.84%	🟡 96%
translate/ spidermonkey	0.00ns	0.00ns	⚪ 0.93%	0.00ns	0.00ns	⚪ -0.25%	🟢 0%
translate/ wasm_kernel	3.80ms	3.79ms	⚪ 0.08%	7.63ms	7.58ms	⚪ -0.55%	🟡 100%

Link to pipeline