[native] [10/40] RN 0.70: Flow update

Summary:
The .flowconfig and package.json changes come from React Native Upgrade Helper. The rest fix Flow errors uncovered by the update.

Historically I've split up Flow changes for a React Native upgrade, but this time there weren't too many!

Depends on D5903

Test Plan: Ran flow and also tested along with whole stack: test plan

Reviewers: tomek, bartek

Subscribers: atul

Differential Revision: https://phab.comm.dev/D5904