Inline reusable allocations

[Robbepop]

This is an experiment to see whether the move overhead of storing reusable allocations by value outweights the indirection overhead of accessing them via reference. Locally I see no significant change in performance, however, so far it seems that the access via reference is by far simpler to setup and use and produces slightly more readable code imo.

These changes might also make it simpler to implement parallel parsing, validation and translation in future versions of wasmi. That means that all functions are parsed, validated and translated in parallel isolation. So far wasmi does not support parallel translation of functions since wasmi is primarily used by us as Wasm binary and Wasm does not (yet) support parallelism.

[paritytech-cicd-pr]

CRITERION BENCHMARKS

BENCHMARK	MASTER	PR	Diff
compile_and_validate_v1	6.5089 ms	6.4134 ms	🟢 -1.3908%
execute_count_until_v1	2.0792 ms	2.0752 ms	⚪ -0.1512%
execute_factorial_iterative_v1	1.6720 µs	1.6610 µs	⚪ -1.0263%
execute_factorial_recursive_v1	2.2286 µs	2.2161 µs	⚪ -0.7885%
execute_fib_iterative_v1	10.136 ms	10.143 ms	⚪ +0.0826%
execute_fib_recursive_v1	20.245 ms	20.274 ms	⚪ -0.0241%
execute_global_bump_v1	4.0059 ms	4.2101 ms	🔴 +7.9810%
execute_host_calls_v1	35.444 µs	37.116 µs	🔴 +5.6725%
execute_memory_fill_v1	8.4480 ms	8.4569 ms	⚪ +0.1612%
execute_memory_sum_v1	8.1805 ms	8.2532 ms	⚪ +0.7257%
execute_memory_vec_add_v1	15.211 ms	15.453 ms	🔴 +1.5848%
execute_recursive_is_even_v1	3.1978 ms	2.8409 ms	🟢 -10.767%
execute_recursive_ok_v1	426.68 µs	389.84 µs	🟢 -8.6657%
execute_recursive_scan_v1	544.41 µs	507.96 µs	🟢 -6.5318%
execute_recursive_trap_v1	40.507 µs	38.129 µs	🟢 -6.1956%
execute_regex_redux_v1	3.5149 ms	3.5158 ms	⚪ +0.0763%
execute_rev_complement_v1	3.0890 ms	3.0907 ms	⚪ +0.1152%
execute_tiny_keccak_v1	2.6719 ms	2.6795 ms	⚪ +0.2335%
execute_trunc_f2i_v1	3.9734 ms	3.9706 ms	⚪ -0.1456%
instantiate_v1	78.780 µs	77.414 µs	⚪ -1.6288%

Link to pipeline