RN0.63 7/16: iOS updates

Test Plan: I made sure pod install worked, and I made sure I could compile the iOS app in both debug and release modes. I also went through some relevant issues in the react-native-upgrade-helper GitHub repo to make sure there wouldn't be any unexpected issues

Reviewers: palys-swm

Subscribers: KatPo, zrebcu411, Adrian

Differential Revision: https://phabricator.ashoat.com/D317