Improve Wasmtime-like API for wasmi

[Robbepop]

Mirror Wasmtime API more closely:

• Renamed Caller::host_data method to Caller::data.
• Renamed Caller::host_data_mut method to Caller::data_mut.
• Add Extern::ty method and the ExternType type.
• Rename ExportItem to ExportType:
  • Rename the ExportItem::kind method to ty and return ExternType instead of ExportItemKind.
  • Remove the no longer used ExportItemKind entirely.
• The ExportsIter now yields items of the new type Export instead of pairs of (&str, Extern).
• Rename ModuleImport to ImportType.
  • Rename ImportType::item_type to ty.
  • Rename ImportType::field to name.
  • Properly forward &str lifetimes in ImportType::{module, name}.
  • Replace ModuleImportType by ExternType.
• Add new convenience methods to Instance:
  • Instance::get_func
  • Instance::get_typed_func
  • Instance::get_global
  • Instance::get_table
  • Instance::get_memory

[paritytech-cicd-pr]

BENCHMARKS

	NATIVE			WASMTIME
BENCHMARK	MASTER	PR	DIFF	MASTER	PR	DIFF	WASMTIME OVERHEAD
execute/ bare_call_0	1.34ms	1.42ms	🔴 6.02%	1.17ms	1.14ms	🟢 -2.13%	🟢 -20%
execute/ bare_call_0/typed	985.89µs	1.01ms	🔴 2.74%	748.01µs	729.09µs	🟢 -2.27%	🟢 -28%
execute/ bare_call_1	1.44ms	1.45ms	🔴 1.77%	1.44ms	1.42ms	🔴 -2.03%	🟢 -2%
execute/ bare_call_16	2.35ms	2.53ms	🔴 7.77%	4.07ms	4.10ms	🟢 0.70%	🟡 62%
execute/ bare_call_16/typed	1.58ms	1.60ms	⚪ 1.27%	2.36ms	2.32ms	🟢 -1.88%	🟢 45%
execute/ bare_call_1/typed	1.10ms	1.10ms	⚪ 0.28%	1.06ms	1.09ms	🔴 2.17%	🟢 -1%
execute/ bare_call_4	1.59ms	1.65ms	🔴 3.84%	2.05ms	1.97ms	🟢 -3.74%	🟢 19%
execute/ bare_call_4/typed	1.10ms	1.12ms	🔴 1.51%	1.14ms	1.12ms	🟢 -1.92%	🟢 -1%
execute/ br_table	1.17ms	1.09ms	🟢 -5.43%	1.29ms	1.25ms	🟢 -3.39%	🟢 14%
execute/ count_until	682.69µs	710.12µs	🔴 4.12%	2.24ms	2.24ms	⚪ 0.36%	🔴 216%
execute/ factorial_iterative	326.57µs	326.70µs	⚪ 0.02%	907.25µs	908.56µs	⚪ 0.29%	🔴 178%
execute/ factorial_recursive	632.93µs	637.19µs	⚪ 0.60%	1.38ms	1.37ms	⚪ -1.04%	🔴 114%
execute/ fib_iterative	1.45ms	1.87ms	🔴 28.32%	4.68ms	4.68ms	⚪ -0.16%	🔴 151%
execute/ fib_recursive	5.75ms	5.75ms	⚪ 0.04%	12.24ms	12.23ms	⚪ -0.59%	🔴 113%
execute/ global_bump	990.44µs	1.02ms	🔴 2.52%	3.32ms	3.32ms	⚪ 0.05%	🔴 227%
execute/ global_const	742.72µs	718.61µs	🟢 -3.06%	2.58ms	2.58ms	⚪ 0.00%	🔴 259%
execute/ host_calls	29.44µs	29.18µs	⚪ -0.79%	43.36µs	41.42µs	🟢 -4.28%	🟢 42%
execute/ memory_fill	1.30ms	1.30ms	⚪ 0.05%	3.98ms	3.99ms	⚪ 0.64%	🔴 206%
execute/ memory_sum	1.27ms	1.30ms	🔴 2.45%	3.95ms	3.95ms	⚪ -0.16%	🔴 203%
execute/ memory_vec_add	2.57ms	2.55ms	⚪ -0.86%	8.25ms	8.23ms	⚪ -0.33%	🔴 222%
execute/ recursive_is_even	1.16ms	1.14ms	⚪ -1.11%	2.34ms	2.24ms	🟢 -4.39%	🟡 96%
execute/ recursive_ok	148.01µs	150.38µs	🔴 1.54%	325.06µs	312.90µs	🟢 -3.66%	🔴 108%
execute/ recursive_scan	180.40µs	180.96µs	⚪ 0.38%	418.16µs	404.91µs	🟢 -2.99%	🔴 124%
execute/ recursive_trap	14.37µs	14.42µs	⚪ 0.34%	31.81µs	31.70µs	⚪ -0.41%	🔴 120%
execute/ regex_redux	537.26µs	539.60µs	⚪ 0.49%	1.48ms	1.48ms	⚪ -0.34%	🔴 174%
execute/ rev_complement	506.77µs	488.53µs	🟢 -3.60%	1.41ms	1.42ms	⚪ 0.55%	🔴 190%
execute/ tiny_keccak	372.46µs	361.35µs	🟢 -2.86%	1.16ms	1.17ms	⚪ 0.92%	🔴 225%
execute/ trunc_f2i	907.82µs	908.50µs	⚪ 0.04%	2.50ms	2.51ms	⚪ 0.13%	🔴 176%
instantiate/ wasm_kernel	63.64µs	67.93µs	⚪ 2.72%	106.07µs	107.20µs	⚪ 0.00%	🟡 58%
translate/ erc1155	210.32µs	210.91µs	⚪ 0.39%	405.77µs	403.83µs	⚪ -0.30%	🟡 91%
translate/ erc20	103.41µs	103.16µs	⚪ 0.33%	199.22µs	203.02µs	⚪ 1.60%	🟡 97%
translate/ erc721	148.44µs	147.18µs	⚪ -1.11%	290.53µs	295.34µs	⚪ 14.96%	🔴 101%
translate/ spidermonkey	0.00ns	0.00ns	⚪ -0.25%	0.00ns	0.00ns	⚪ 1.73%	🟢 0%
translate/ wasm_kernel	3.82ms	3.77ms	⚪ -0.66%	7.82ms	7.99ms	🔴 2.47%	🔴 112%

Link to pipeline