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/consensus/pow/src/worker.rs

@@ -169,7 +169,7 @@ where
 				Err(err) => {
 					warn!(
 						target: "pow",
-						"Unable to import mined block: {:?}",
+						"Unable to import mined block: {}",
 						err,
 					);
 					return false
@@ -238,7 +238,7 @@ where
 			Err(err) => {
 				warn!(
 					target: "pow",
-					"Unable to import mined block: {:?}",
+					"Unable to import mined block: {}",
 					err,
 				);
 				false