Flushing out the new API

[jamesdaniels]

• Adding ScreenTrackingService and UserTrackingService for the new API
• Injectable classes should all be implicitly optional, since I can't figure out how to bail from the factory
• Drop the memoization as the modules are idempotent in v9
• Return null from analytics and messaging when they're incompatible, rather than a null object
• Now test for browser and return null otherwise for remote config and performance
• Allow more advanced initialization in provide* by allowing the developer to pass deps into the N+1 args & use the injector in the factory
• Use AppCheck debug token if they're serving off localhost too, e.g, ng deploy --preview
• Upgrade Firebase to 9.1
• Utilize isSupported for Remote Config

Follow on:

• Add the auth guards
• Flush out new performance API
• Flush out new RC API
• Flush out new analytics API
• Flush out new messaging API
• Add the storgae pipe into the new API
• Make sure compat + new API play well together