Currently flutter.js nags users in the console if the Service worker not supported (or configured).

We have received several issues, and internal feedback about this:

• Flutter Web Hot Reload Error - Service Worker Not Supported #113145
• [web][iOS] Error: Web Service worked not supported (or configured) in Safari browser on Iphone SE #109771

We should NOT warn users in case that serviceWorker == null (the "(or configured)" part), just noop silently. A blank serviceWorker config is a sign that the user does NOT want to use our serviceWorker, not an issue.

We also should check: isSecureContext to tell users why the ServiceWorker may not be available, and point them to some documentation.

/cc @jacobsimionato