Various fixes, mostly ng10 and FCM regressions

[jamesdaniels]

• Use navigator serviceWorker for notifications, as FCM seems to be having trouble with RXJS & Angular
• Use more of the registerX hacks to work around ngcc tree-shaking. Tapping also seems to help, race condition maybe?
• Port the sample app to NG 10
• Add all the firebase packages to the Universal externals, having a bunch of problems with that
• Experimenting with overriding the legacy packaging choices of the JS SDK with ngcc.config in the sample app, should add to the ng add schematic if it proves workable
• FCM broke in a minor at some point, getToken now prompts for permission; work around this break for now
• Firebase Auth seems to be firing an initial null more often now, add the getRedirectResult work-around for now
• Firebase Auth is now failing to load in the server environment entirely, work around by returning of(null)
• Storage is not firing the last snapshot state before completion, making this API difficult to work with, fixed