Add a new host function for reporting fatal errors; make WASM backtraces readable when printing out errors (#10741)

* Add a new host function for reporting fatal errors

* Fix one of the wasmtime executor tests

* Have `#[runtime_interface(wasm_only)]` actually mean WASM-only, and not no_std-only

* Print out errors through `Display` instead of `Debug`

* Switch one more trait to require `Error` for its error instead of only `Debug`

* Align to review comments

substrate/client/finality-grandpa/src/import.rs

@@ -598,7 +598,7 @@ where
 				Err(e) => {
 					debug!(
 						target: "afg",
-						"Restoring old authority set after block import error: {:?}",
+						"Restoring old authority set after block import error: {}",
 						e,
 					);
 					pending_changes.revert();
@@ -663,8 +663,12 @@ where
 
 				import_res.unwrap_or_else(|err| {
 					if needs_justification {
-						debug!(target: "afg", "Imported block #{} that enacts authority set change with \
-							invalid justification: {:?}, requesting justification from peers.", number, err);
+						debug!(
+							target: "afg",
+							"Requesting justification from peers due to imported block #{} that enacts authority set change with invalid justification: {}",
+							number,
+							err
+						);
 						imported_aux.bad_justification = true;
 						imported_aux.needs_justification = true;
 					}