[native] [3/40] RN 0.70: iOS stuff

Summary:
These are the non-Podfile iOS changes from React Native Upgrade Helper. The project.pbxproj parts had to be "reverse engineered" from the patch there and then manually reapplied using Xcode... since those are pretty complicated, I'll try to describe inline.

Depends on D5896

Test Plan: Tested along with whole stack: test plan

Reviewers: tomek, bartek

Subscribers: atul

Differential Revision: https://phab.comm.dev/D5897