Make debug builds more usable (#4683)

* Make debug builds more usable

This pr makes debug builds more usable in terms of `cargo run -- --dev`.

1. `--dev` activates `--execution native`, iff `--execution` is not
given or no sub `--execution-*` is given.
2. It was probably a mistake to compile WASM in debug for a debug build.
So, we now build the WASM binary always as `release` (if not requested
differently by the user). So, we trade compilation time for a better
debug experience.

* Make sure we only overwrite default values

* Make it work

* Apply suggestion

substrate/utils/wasm-builder/src/wasm_project.rs

@@ -357,7 +357,7 @@ fn is_release_build() -> bool {
 			),
 		}
 	} else {
-		!build_helper::debug()
+		true
 	}
 }