firebase-ios-sdk

Add a completion handler to FIRExperimentController's updateExperimentsWithServiceOrigin: method (#4897)

* Add completion handler to FIRExperimentController updateExperimentsWithServiceOrigin:

* Update tests to verify completion handler is called

* Add error param to the completion handler in updateExperimentsWithServiceOrigin:

* Rename error domain for ABT SDK  errors, rename method to set CUPs via the user property controller-- it doesn't do anything in the background

* Add back support for updateExperiments method without completion

* Add description for Failed to get conditional user properties error

* Fix string argument warning

* Deprecate updateExperimentsWithServiceOrigin method that doesn't have a completion handler

* Ignore deprecated warning in tests

* Run scripts/styles.sh