Separate wasmi and wasmer sandbox implementations into their own modules (#10563)

* Moves wasmi specific `ImportResolver` and `MemoryTransfer` impls to submodule

* Splits context store environmental, moves impl `Externals` to wasmi backend

* Adds wasmer sandbox backend stub module

* Move sandbox impl code to backend specific modules

* Moves wasmi stuff

* Fixes value conversion

* Makes it all compile

* Remove `with_context_store`

* Moves `WasmerBackend` to the impl

* Reformat the source

* Moves wasmer MemoryWrapper

* Reformats the source

* Fixes mutability

* Moves backend impls to a submodule

* Fix visibility

* Reformat the source

* Feature gate wasmer backend module

* Moves wasmi memory allocation to backend module

* Rename WasmerBackend to Backend

* Refactor dispatch result decoding, get rid of Wasmi types in common sandbox code

* Reformat the source

* Remove redundant prefixes in backend functions

* Remove wasmer-sandbox from default features

* Post-review changes

* Add conversion soundness proof

* Remove redundant prefix

* Removes now redundant clone_inner

* Add `Error::SandboxBackend`, refactor invoke result

* Fix comments

* Rename `Error::SandboxBackend` to `Sandbox`

* Simplifies logic in `wasmer_backend::invoke`

* Fixes memory management

substrate/client/executor/wasmi/src/lib.rs

@@ -102,10 +102,7 @@ impl<'a> sandbox::SandboxContext for SandboxContext<'a> {
 		match result {
 			Ok(Some(RuntimeValue::I64(val))) => Ok(val),
 			Ok(_) => return Err("Supervisor function returned unexpected result!".into()),
-			Err(err) => Err(Error::AbortedDueToTrap(MessageWithBacktrace {
-				message: err.to_string(),
-				backtrace: None,
-			})),
+			Err(err) => Err(Error::Sandbox(err.to_string())),
 		}
 	}
 
@@ -222,7 +219,6 @@ impl Sandbox for FunctionExecutor {
 		let args = Vec::<sp_wasm_interface::Value>::decode(&mut args)
 			.map_err(|_| "Can't decode serialized arguments for the invocation")?
 			.into_iter()
-			.map(Into::into)
 			.collect::<Vec<_>>();
 
 		let instance =