Runtime logging. (#3821)

* Implement Printable for tuples.

* Add debugging function.

* Add debug 1.

* Implement  for everything.

* RuntimeDebug derive.

* Introduce RuntimeDebug.

* Add some dummy logging.

* Replace RuntimeDebug with Debug.

* Revert "Replace RuntimeDebug with Debug."

This reverts commit bc47070a8cb30241b2b590b2fa29fd195088162f.

* Working on Debug for all.

* Fix bounds.

* Add debug utils.

* Implement runtime logging.

* Add some docs and clean up.

* Clean up derives.

* Fix custom derive impl.

* Bump runtime.

* Fix long lines.

* Fix doc test.

* Use CARGO_CFG_STD.

* Revert "Use CARGO_CFG_STD."

This reverts commit ea429566de18ed0fa052571b359eb9826a64a9f4.

* Use parse_macro_input

* Update lockfile.

* Apply review suggestions.

* Remove stray re-export.

* Add no-std impl.

* Update lockfile.

substrate/core/sr-io/with_std.rs

@@ -192,6 +192,22 @@ impl OtherApi for () {
 	fn print_hex(data: &[u8]) {
 		println!("{}", HexDisplay::from(&data));
 	}
+
+	fn log(
+		level: LogLevel,
+		target: &[u8],
+		message: &[u8],
+	) {
+		let target = std::str::from_utf8(target).unwrap_or("invalid utf8");
+		let msg = std::str::from_utf8(message).unwrap_or("invalid utf8");
+
+		log::log!(
+			target: target,
+			log::Level::from(level),
+			"{}",
+			msg,
+		)
+	}
 }
 
 impl CryptoApi for () {