* Remove FIRAnalyticsConfiguration from Public header.
We haven't removed it entirely yet because we need to make changes
within Analytics to verify that the global data collection switch is
still honored and tested well. This can wait until after the breaking
change because the header and code will be internal after this change.
* Fixed incomplete comment.
* Remove self importing header.
* Better mocking for Core Unit Tests
This includes NSNotificationCenter and NSUserDefaults to prevent
flaky tests and unit tests interfering with each other.
* Share variable for intervals being set.
Ryan Wilson