added react native feature flags (#22199)

lunaruan commented 3 days ago • 
This PR adds separate DevTools feature flag configurations for react-devtools-core. It also breaks the builds down into facebook specific and open source flags so we can experiment in React Native.

Tested yarn build:standalone, yarn build:backend, yarn build:standalone:fb, and yarn build:backend:fb and inspected the output to make sure each package used the correct feature flags (the first two use core-oss and the latter two use fb-oss.