Integrate Wasmtime for runtime execution (#3869)

* executor: Use non wasmi-specific execution in tests.

* executor: Move all runtime execution tests into tests file.

* executor: Use test_case macro to easily execute tests with different
Wasm execution methods.

* executor: Convert errors to strings with Display, not Debug.

* node-executor: Rewrite benchmarks with criterion.

They were not passing compilation before and criterion seems to be more
widely used in Substrate.

* executor: Begin implementation of Wasm runtime.

The implementation demonstrates the outline of the execution, but does
not link against the external host functions.

* executor: Define and implement basic FunctionExecutor.

The SandboxCapabilities::invoke is still left unimplemented.

* executor: Implement host function trampoline generation.

* executor: Instantiate and link runtime module to env module.

* executor: Provide input data during wasmtime execution.

* executor: Implement SandboxCapabilites::invoke for wasmtime executor.

* executor: Integrate and test wasmtime execution method.

* executor: Improve FunctionExecution error messages.

* Scope the unsafe blocks to be smaller.

* Rename TrampolineState to EnvState.

* Let EnvState own its own compiler instead of unsafe lifetime cast.

* Refactor out some common wasmi/wasmtime logic.

* Typos and cosmetic changes.

* More trampoline comments.

* Cargo.lock update.

* cli: CLI option for running Substrate with compiled Wasm execution.

* executor: Switch dependency from fork to official wasmtime repo.

* Quiet down cranelift logs.

* Explicitly catch panics during host calls.

We do this to ensure that panics do not cross language boundaries.

* Additional checks and clarifications in make_trampoline.

* Fixes after merge from master and panic safety for wasmtime
instantiation.

substrate/core/cli/src/params.rs

@@ -50,6 +50,19 @@ arg_enum! {
 	pub enum WasmExecutionMethod {
 		// Uses an interpreter.
 		Interpreted,
+		// Uses a compiled runtime.
+		Compiled,
+	}
+}
+
+impl WasmExecutionMethod {
+	/// Returns list of variants that are not disabled by feature flags.
+	fn enabled_variants() -> Vec<&'static str> {
+		Self::variants()
+			.iter()
+			.cloned()
+			.filter(|&name| cfg!(feature = "wasmtime") || name != "Compiled")
+			.collect()
 	}
 }
 
@@ -57,6 +70,12 @@ impl Into<service::config::WasmExecutionMethod> for WasmExecutionMethod {
 	fn into(self) -> service::config::WasmExecutionMethod {
 		match self {
 			WasmExecutionMethod::Interpreted => service::config::WasmExecutionMethod::Interpreted,
+			#[cfg(feature = "wasmtime")]
+			WasmExecutionMethod::Compiled => service::config::WasmExecutionMethod::Compiled,
+			#[cfg(not(feature = "wasmtime"))]
+			WasmExecutionMethod::Compiled => panic!(
+				"Substrate must be compiled with \"wasmtime\" feature for compiled Wasm execution"
+			),
 		}
 	}
 }
@@ -429,7 +448,7 @@ pub struct RunCmd {
 	#[structopt(
 		long = "wasm-execution",
 		value_name = "METHOD",
-		possible_values = &WasmExecutionMethod::variants(),
+		possible_values = &WasmExecutionMethod::enabled_variants(),
 		case_insensitive = true,
 		default_value = "Interpreted"
 	)]