Extensions allow declarative extensions to "JsRuntime" (ops, state, JS or middleware).
This allows for:
- `op_crates` to be plug-and-play & self-contained, reducing complexity leaked to consumers
- op middleware (like metrics_op) to be opt-in and for new middleware (unstable, tracing,...)
- `MainWorker` and `WebWorker` to be composable, allowing users to extend workers with their ops whilst benefiting from the other infrastructure (inspector, etc...)
In short extensions improve deno's modularity, reducing complexity and leaky abstractions for embedders and the internal codebase.
Change `Console.#printFunc` to pass a log level as the second argument
(0 = debug, 3 = error), instead of a boolean for `isErr`. This does not
change the Deno runtime behaviour at all.
