firebase-ios-sdk

Fix component startup time. (#4137)

* Fix component startup time.

The `configureWithApp:` call shouldn't have been added - the
component registration system can provide proper configuration
instead of relying on a static `configureWithApp:` call. Many of
the SDKs relied on singletons being available there, which wasn't
necessary. Instead, this should happen in the component creation
block and use the instantiationTiming parameter on
registerInternalLibrary.

* Fix missing `nil` statement.